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o  PreTinger 

i     a 

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FIRST  PRINCIPLES 


CHEMIST  RY, 

<t 


FOB   THE   USB  OT 


COLLEGES  A^D  'SCHOOLS. 


BY  BENJAMIN  SILLIMAN,  JR.,  M.  A. 

PROFKSSOli    IN   YAX.K   COLLEGE   OF   CHEMISTRY   AS   APPLIED    TO   THE   ARTS. 


WITH  MORE  THAN  TWO  HUNDRED  ILLUSTRATIONS, 


•.  -*t 


.• 


SEVENTH  THOUSAND. 


PHILADELPHIA: 

PUBLISHED    BY    LOOMIS  &    PECK 
NEW-HAVEN :  DURR1E  &  PECK. 

1848. 


Entered  according  to  Act  of  Congress,  in  the  year  181G,  by 

L  O  O  M  I  S    A:     P  E  C  K  , 
in  the  Clerk's  Office  of  the  District  Court  of  Connecticut. 


K.   B.    MEARS,    STEKEOTYI'ER, 
Jhrfs  Ruil  linp,  N.  K.  cnrm-r  of  Suth  and  Cbeinut. 

SMITH    AND    PETERS,    PRINTERS, 
Franklin  BuiMinp,  Sixth  street  U-!o.v  Arch,  Philnlrlphii. 


.r:-ow 


«"   •--   v»i 


^.. 


TO 

PROFESSOR  SILLIMAN, 

i 

THIS     V  O  L  U  M  E  ,    r'   I ' 

DESIGNED 

TO    PROMOTE    THE    CAUSE    OF    SCIENCE, 

TO    WHICH    HE    HAS    DEVOTED    HIS    LIFE, 

IS   RESPECTFULLY   DEDICATED, 

BY   HIS   SON, 


THE  AUTHOR, 

ff  J,  A 


PREFACE  TO  THE  SECOND  EDITION. 

THE  sale  of  the  first  edition  of  three  thousand  copies  of  this  work 
in  the  space  of  a  few  months,  has  required  the  preparation  of  a  new 
edition  at  an  earlier  date  than  was  originally  anticipated.  Every 
part  of  the  book  has  been  thoroughly  revised  and  corrected,  and 
some  portions  have  been  entirely  rewritten.  At  the  same  time, 
the  author  has  desired  to  avoid  the  common  error  of  making  unim- 
portant changes,  which  serve  only  to  annoy  teachers  who  already 
use  the  book. 

The  ORGANIC  CHEMISTRY  has  been  entirely  rewritten  (with  the 
exception  of  the  last  twenty  pages),  by  the  same  able  hand  that 
prepared  it  in  the  first  edition.  It  is  believed  that  this  change  will 
give  great  satisfaction  to  all  who  are  not  tied  by  prejudice  to  the 
theory  of  organic  radicals — those  ideal  creations,  which,  with  the 
appearance  of  simplicity,  really  encumber  us  with  a  load  of  unreal 
knowledge.  The  simpler  and  more  truthful  philosophy  of  the  new 
French  school,  which  is  now  for  the  first  time  presented  in  an  ele- 
mentary form,  will,  it  is  believed,  be  soon  generally  adopted. 

The  adoption  of  this  work  by  many  of  the  first  seminaries  of 
learning  in  this  country,  is  a  gratifying  evidence  to  the  author  that 
his  design  has  been  appreciated ;  and  he  trusts  that  those  who  gave 
their  confidence  to  the  first  edition,  will  find  the  present  one,  in 
some  important  respects,  superior  to  it. 

As  the  work  is  now  stereotyped,  it  must  remain  in  its  present 
form  until  the  progress  of  the  science  requires  it  to  be  again  re- 
modeled. 

YALK  COLLEGE,  NEW  HA  VEX,  Ct.          ) 
Analytical  Laboratory,  Sept.  15, 1847.  > 


FROM  THE  PREFACE  TO  THE  FIRST  EDITION. 

THE  object  of  this  work  is  sufficiently  indicated  by  its  title.  It 
has  grown  out  of  the  exigencies  of  teaching,  and  has  been  received 
as  the  Text  Book  in  the  public  lectures  at  Yale  College. 

It  is  important  that  a  work  of  this  kind  should  contain  only  such 
matter  as  is  actually  taught  to  a  class  by  recitations  and  lectures. 
1* 


VI  PREFACE. 

All  fulness  beyond  this  is  unavailable  to  either  teacher  or  pupil, 
and  serves  often  to  embarrass  the  one  and  to  discourage  the  other. 
This  is  perhaps  the  reason  why  several  works,  otherwise  excellent, 
have  failed  to  answer  the  purpose  for  which  they  were  written. 
The  science  of  Chemistry  has  now  reached  the  point  where  its 
First  Principles  can  be  presented  by  the  teacher  with  almost  mathe- 
matical precision. 

Chemistry  has  attractions  of  an  economical  and  experimental 
character,  which  will  always  secure  for  it  a  place  in  every  system 
of  education.  Without  wishing  to  diminish  its  claims  to  attention 
on  these  grounds,  the  author  urges  the  paramount  advantages  pos- 
sessed by  his  favorite  science,  as  a  study  peculiarly  fitted  to  train 
the  mind  to  a  methodi/.ed  and  logical  habit  of  thought.  If  nothing 
more  is  to  be  derived  from  its  study  than  the  entertainment  offered 
by  brilliant  phenomena,  and  a  knowledge  of  convenient  economical 
processes,  the  pupil  will  fail  of  its  most  important  advantage.  The 
beautiful  philosophy,  the  perspicuous  nomenclature,  and  lucid 
method  of  modern  chemistry,  are  so  obvious  that  they  cannot  fail 
to  awaken  the  attention  of  every  intelligent  pupil,  and  carry  him 
on  his  course  of  intellectual  culture  with  rapid  progress.  *  *  *  * 

The  author  has  consulted  all  the  best  authorities  within  his  reach, 
both  in  the  standard  systems  of  England  and  France,  and  in  the 
scientific  journals  of  this  country  and  Europe.  The  works  of  Dan- 
iell,  Graham,  Brande,  Kane,  Fownes,  Gregory,  Faraday,  Mitscher- 
lich,  Berzelius,  Dumas,  Liebig,  and  Gerhardt,  have  all  been  used,  as 
also  the  treatises  of  Dr.  Hare  and  Prof.  Silliman. 

The  Organic  Chemistry  is  presented  mainly  in  the  order  of  Lie- 
big  in  his  Traite  tie  Chimie  Organiqttf.  The  author  takes  pleasure 
in  acknowledging  the  important  aid  derived  in  this  portion  of  the 
work  from  his  friend  and  professional  assistant,  Mr.  THOMAS  S. 
HUNT,  whose  familiarity  with  the  philosophy  and  details  of  Chem- 
istry, will  not  fail  to  make  him  one  of  its  ablest  followers.  The 
labor  of  compiling  the  Organic  Chemistry  has  fallen  almost  solely 
upon  him.  ••••••• 

If  it  shall  be  found  to  meet  the  wants  of  both  teachers  and  pupils, 
and  to  promote  the  progress  of  Scientific  Chemistry  in  this  coun- 
try, the  author  will  feel  that  he  has  not  labored  in  vain. 

NEW  HAVEN,  December  1,  1646. 


TABLE  OF  CONTENTS. 


INTRODUCTION, 

Sources  of  Knowledge, 

Distinction  between  the  an- 
cient and  modern  philo- 
sophy, . 

Physical  and  Intellectual 
Philosophy, 

General   divisions   of 

knowledge  of  nature, 
MATTER. — General  Properties 
of  Matter, 

Molecules,  or  Atoms, 

Indestructibility  of  Matter, 
and  Cohesion, 

Repulsion    and 
Attraction, 

Elements  and  Impondera- 
ble Agents, 

The  Three  States  of  Mat- 
ter—the Solid,  the  Flu- 
id, and  the  Gaseous, 

The  Atmosphere  and  Laws 
of  Gases, 

Air-Pump, 

Law  of  Mariotte, 

Barometer, 

Limits  of  the  Atmosphere, 

Weight  and  Specific  Gra- 
vity, 

Standards  of  Specific  Gra- 
vity, 


PART  I. 
PHYSICS. 

PAGE                                                                                            PAOK 

. 

n 

Specific  Gravity  of  Solids,   30 

e» 

L3 

The  Hydrometer,         .         39 

lean- 

Specific  Gravity  of  Gases,    41 

ihilo- 

LIGHT,  Sources  and  Nature,      41 

11 

Reflection,  ...         43 

ctual 

Refraction,           .          .         44 

. 

14 

Prism    and    Analysis    of 

our 

Light,      ...         46 

e, 

15 

Double  Refraction,       .         48 

jrties 

Polarization,        .          .         49 

. 

18 

Chemical  Rays,  .         .         50 

17 

Spectral  Impressions,  .         51 

atter, 

Phosphorescence,         .         52 

18 

HEAT  —  Sources,        .         .         53 

mical 

Expansion,           .         .         55 

19 

Thermometers,    .         .         56 

dera- 

Pyrometers,         .         .         62 

. 

20 

Laws  of  Expansion,     .         63 

Mat- 

Unequal  Expansion  of  Wa- 

Flu- 

ter,           ...         65 

5, 

21 

Communication  of  Heat,       67 

Laws 

Conduction,          .          .         68 

§ 

21 

Convection  of  Heat,    .         71 

. 

26 

Radiant  Heat,      .         .         72 

. 

27 

Absorption,          .         .         73 

29 

Transmission  of  Heat,          74 

>here, 

32 

Melloni's  Experiments,        75 

Gra- 

Specific  Heat  or  Capacity,  78 

. 

33 

Changes  produced  by  Heat 

Gra- 

in   the  State  of  Bodies, 

. 

34 

Liquefaction,    .         .         79 

quids, 

35  |        Freezing  and  Melting,    81,  52 

Vlll 


CONTENT:?. 


Vaporization,       (Boiling- 

Points,)  ...  83 
Cryophorus,  .  .  87 
Elevation  of  Boiling-Points 

by  Pressure,    .         .         88 
The  Steam  Engine,      .         90 
Evaporation,        .         .         90 
Maximum  Density  of  Va- 
pors,       ...         91 
Diffusion  of  Gases,       .         92 
Dew  Point,          .         .         93 . 
Hygrometers,      .         .         94 
Spheroidal  State  of  Bodies,    95 
Liquefaction  of  Gases,     95,  96  j 
ELECTRICITY. — Of  Magnetism,  98  , 
Magnetics    and    Diamag- 

netics,      .         .         .       102  | 
Electricity  of  Fnction,       103 
Theories  of  Electricity,      105 


PACK 

Electroscopes,  .  .  106 
Electrical  Machines,  .  107 
Leyden  Jar  and  Electro- 

phorous,  .         .       108 

Electricity   of    Chemical 

Action — Galvanism,  109 
Voltaic  Pile,  .  .  Ill 
Simple  Voltaic  Circle,  112 
Compound  Voltaic  Circle,  113 
Galvanic  Batteries,  .  115 
Electro-Magnetism,  .  116 
Ampere's  Theory,  .  118 
Electro-Magnetic  Motions  121 
Henry's  Coils,  .  .  123 
Secondary  Currents,  .  12 4 
Electro-Magnetic  Tele- 
graph, .  .  .127 
Magneto-Electricity,  .  130 
Thermo-Electricity,  .  131 


PART  II. 


CHEMICAL    PHILOSOPHY. 


ELEMENTS  AND  THEIR  LAWS 

OF  COMBINATION,      .        133 
Combination  by  Weight,     134 
Definite  and  Multiple  Pro- 
portions, .          .          .        134 
Equivalent  Proportions,      135 
Table  of  Chemical  Equi- 
valents,  .         .         .  136-7 
Combination  by  Volume,    138 
Chemical  Nomenclature,     140  I 
Names  of  Compounds,         141 
Chemical  Symbols,      .       145 
Chemical  Affinity,        .       147 
Atomic  Theory,  .         .       151 
Specific  Heat  of  Atoms,      152 

CRYSTALLIZATION,     .         .       152 


Crystalline  forms,        .       155 
Cleavage  of  Crystals,          158 
Measurement     of    Crys- 
tals,         .          .          .159 
Isomorphism,        .  161 

CHEMICAL  EFFECTS  OF  VOL- 
TAIC ELECTRICITY,    .       163 
Conditions  of  Voltaic  De- 
composition,   .         .       164 
Laws  of  Electrolysis,  .       167 
Voltameters,        .         .       168 
Sustaining  Batteries,    .       169 
"  "  Daniell's,  170 

Grove's  and  Smee's  Bat- 
teries,     .         .         .171 
Electro-Metallurgy,     .       173 


CONTENTS. 


PART  HI. 
INORGANIC    CHEMISTRY. 


PAGE 

NON-METALLIC  ELEMENTS,      175 
Classification,     .         .        175 

1.  Oxygen,    ...        176 
Management  of  Gases,       179 

2.  Chlorine,  ...        181 
Compounds   of   Chlorine 

with  Oxygen,          .        185 

3.  Bromine,  .         .         .        188 

4.  Iodine,       .         .         .        189 
Compounds  of  Iodine  with 

Oxygen,  &c.  .         .        190 

5.  Fluorine,  ...         191 

6.  Sulphur,    ...        192 
Compounds  with  Oxygen,  193 
Sulphurous  Acid,        .         194 
Sulphuric  Acid,  .        195 

7.  Selenium,  ...        199 

8.  Tellurium,          .         .        200 

9.  Nitrogen,  ...        200 
Chemical  History  of  the 

Atmosphere,  .  .  202 
Compounds  of  Oxygen 

and  Nitrogen,  .  203 
Nitrous  Oxyd,  .  .  204 
Nitric  Oxyd,  .  .  205 
Nitric  Acid,  .  .  207 

10.  Phosphorus,        .         .        209 
Compounds  of  Phospho- 
rus with  Oxygen,  .        211 

Other  Compounds  of  Phos- 
phorus, .         .        212 

11.  Carbon,      ...        213 
Carbonic  Acid,  .        217 
Carbonic  Oxyd,  .        220 
Compounds     of    Carbon 

with  the  Chlorine  Group,  222 
Compounds  of  Carbon  and 


Nitrogen, 

12.  Silicon,      . 
Sicilic  Acid, 
Fluorid  of  Silicon, 

13.  Boron, 
Boracic  Acid,    . 

14.  Hydrogen, 


222 
223 
224 
226 
227 
228 
229 


PAOK 

Nature  of  Hydrogen,          234 
Compounds  of  Hydrogen,  235 
Water,       .         .         .        235 
Eudiometry  by  Hydrogen,  240 
Union  of  Hydrogen  and 
Oxygen    by    platinum 
sponge,  .         .         .        241 
Oxyhydrogen  Blowpipe,    242 
Natural  and  Chemical  His- 
tory of  Water,         .    ,    244 
Peroxyd  of  Hydrogen,       246 
Ozone,       ...        247 
Compounds  of  Hydrogen 

with  II.  and  III.  classes,  248 
Action  of  Hydrogen  with 

Chlorine,  .  .  248 
Hydrochloric  Acid,  .  249 
Hydrobromic  Acid,  .  252 
Hydriodic  Acid,  .  253 
Hydrofluoric  Acid,  .  254 
Hydrosulphuric  Acid,  255 
Ammonia,  .  .  258 
Phosphureted  Hydrogen,  261 
Light  Carbureted  Hydro- 
gen, ...  263 
Olefiant  Gas,  .  .  264 
Combustion  and  Structure 

of  Flame,        .         .        266 

Lamps  and  Blowpipe,    271-2 

Safety  Lamp,     .         .        274 

METALLIC  ELEMENTS,       .        275 

General  Properties  of  the 

Metals,.  .  .  276 
Classification  of  Oxyds,  278 
Theory  of  Salts,  .  279 
Classification  of  Metals,  281 

15.  Potassium,          .         .        282 
Potash,      ...        284 
Salts  of  Potash,          .        287 

16.  Sodium  and  Soda,       .        292 
Chlorid,  &c.  of  Sodium,     293 
Manufacture  of  Glass,        297 

17.  Ammonium,       .         .        298 
Salts  of  Ammonium,  .        299 


CONTENTS. 


Hydrosnlphuret   of  Am- 
monia,  . 

18.  Lithium,    . 

19.  Barium,     .         .    "     . 

20.  Strontium, 

21.  Calcium  and  Lime,    . 

22.  Magnesium  and  Magnesia,  306 

23.  Aluminium, 
Alums, 
Pottery,     . 

24.  Glucinum;    25.  Yttrium  ; 

26.  Zirconium;  27. 
Thorium;  28.  Cerium; 
29.  Lantanum, 

30.  Manganese, 

31.  Iron, 

Manufacture  of  Iron, . 
Oxyds  of  Iron,  . 

32.  Chromium, 

33.  Nickel,       . 

34.  Cobalt,       . 

35.  Zinc, 

36.  Cadmium, 


'AGE 

PAG* 

37. 

Lead, 

. 

324 

300 

38. 

Uranium, 

.         . 

326 

301 

39. 

Copper, 

. 

326 

3QJ 

40. 

Vanadium 

;  41.  Tungsten; 

303 

42.  Molybdenum  ;  43.  Co- 

303 

lumbium  ; 

44.  Titanium, 

327 

306 

45. 

Tin, 

.         . 

329 

308 

46. 

Bismuth, 

,         . 

331 

309 

47. 

Antimony 

332 

310 

48. 

Arsenic, 

. 

334 

Arsenious 

Acid,    White 

Arsenic 

»          •         • 

334 

Detection 

of  Arsenic  as  a 

311 

poison, 

. 

336 

312 

49. 

Osmium, 

... 

338 

314     50. 

Mercury, 

. 

339 

315    51. 

Silver, 

... 

342 

316 

52. 

Gold, 

... 

345 

318 

53. 

Platinum, 

•         • 

346 

320    54. 

Palladium 

348 

321 

55. 

Rhodium, 

... 

349 

322 

56. 

Iridium, 

. 

349 

323 

PART  IV. 
ORGANIC    CHEMISTRY. 


INTRODUCTION,          .         .        350 
General  Properties  of  Or- 
ganic Bodies,  .        350 
Modes  of  Combination,       352 
Equivalent  Substitution,     352 
Monobasic     Acids,     and 
Substitution    by    Resi- 
dues,     .         .         .        353 
Sesqui-salts,  Direct  Union,  354 
Isomerism,          .         .        354 
On  the  Density  of  Vapors,  355 
Analysis  of  Organic  Sub- 
stances,          .         .        357 
ORGANIC  COMPOUNDS  AND  PRO- 
DUCTS OF  THEIR  ALTERA- 
TION,          .         .         .        362 
Ammonia,  .          .         .        362 


Amides,     .         .         .        363 
THE  GROUP  OF  ALCOHOLS, 

Alcohol,     ...        364 
Sulphur  Alcohol,         .        366 
Action  of  Acids  upon  Al- 
cohol,    .         .         .        366 
Coupled  Acids,  .         .        367 
Nitric,  Perchloric,  Hydro- 
chloric Ethers,        .  368-69 
Acetene,  Nitric   Acetene, 

Sulphovinic  Acid,     369-70 
Carbovinic  Acid,         .        370 
Silicic    Ethers,    Products 
of    the    decomposition 
of  Sulphovinic  Acid,       371 
Sulphuric  Ether,  Letheon,  372 
Olenant  Gas,       .         .        373 


CONTENTS. 


PAGE 

Dutch  Oil,          .         .        374 
Products   of   the  Oxyda- 

tion  of  Alcohol,  .  375 
Acetic  Acid,  .  .  376 
Acetates,  .  .  377 

Acetates  of  Lead,       .       378 
Wood-Spirit,  or  Methylic 

Alcohol,  .  .  380 
Methylic  Ethers,  &c.,  381 
Oxydation  of  Wood-Spirit,  382 
Formic  Acid,  .  .  383 
Amylic  Alcohol,  .  383 
Amy  lie  Ethers,  .  .  384 
Oxydation  of  Amylic  Acid,  385 
Ethal  and  Ethalic  Acid,  385-6 
On  the  Relations  of  the 

preceding  Bodies,  .  387 
Bitter  Almond  Oil,  Ben- 

zoilol,  .  .  .388 
Benzamide,  Hydrobenza- 

mide,  .  .  .  389 
Benzoine,  Benzene,  Nitro- 
benzene, .  .  390 
Oil  of  Cumin,  .  .  390 
Oil  of  Spirea,  .  .  391 
Salicylol,  Salicylic  Acid,  391 
Phenol,  Oil  of  Cinnamon,  393 
SUGAR,  STARCH,  AND  ALLIED 
SUBSTANCES,  .  .  394 
Products  of  the  decompo- 
sition of  the  Sugars,  395 
The  Vinous  Fermentation,  395 
Lactic  Acid,  .  .  396 
Starch,  .  .  .398 
Dextrine,  .  .  .399 
Woody  Fibre,  .  .  400 
Xyloidine,  Gun  Cotton, 


Pyroxyline, 


401 


Transformation  of  Woody 
Fibre,  Destructive  Dis- 
tillation of  Wood,   .        403 
Kreasote,  Paraffine,  Coal 

Tar,        .          .          .404 
Petroleum,          .         .        405 
FATS  AND  THE  SUBSTANCES  DE- 
RIVED FROM  THEM,          .          405 

Soaps,  Glycerides,  Acro- 
leine,  .  .  .  406 

Butyric  Acid,  Butyric 
Ether,  .  .  .407 

Margarine,  Stearrne,  Ole- 
ine,  409 


Fatty  Acids, 
Oleic  Acid, 
Soaps, 

VEGETABLE  ACIDS,  . 
Oxalic  Acid, 
Oxalate  of  Lime, 
Tartaric  Acid,    . 
Racemic,  Malic, 
Citric, 

Tannic,  Tannin, 
Gallic  Acid, 


PAGE 

410 
411 
412 
412 
412 
414 
414 
415 
416 
417 
418 

VOLATILE  OR  ESSENTIAL  OILS,  418 
Oil  of  Turpentine,  .  419 
Camphene,  .  .  419 
Juniper,  Pepper,  Lemon, 

&c.  419 

Camphor,    Borneo    Cam- 
phor, Oil  of  Mustard,     420 
Caoutchouc,  Gum-Elastic,  420 
Gutta  Percha,      .         .        421 
COLORING  MATTERS,          .        421 
Quercitrine,   Carthamine, 

Turmeric,       .         .        422 
Hematoxyline,    Carmine, 
Chlorophyle,    Lecano- 
rine,  Orcine,  .         .        422 
Indigo,        .         .         .423 
Indigogene,  Sulphindigotic 

Acid,  Saxon  Blue,  .  424 
Isatine,  Chlorisatine,  .  425 
Isatyde,  Indine,  Ariilic 

Acid,      .         .         .425 
Chloranile,          .         .       426 
ORGANIC  BASES,  OR  ALKALOIDS. 
Constitution  and  characters  426 
Anilene,  Chloranilene,  Ni- 

traniline,         .         .        427 
Quinoline,   Nicotine,  Co- 
nine, Amarine,        .       428 
Cinchonine,         .         .       428 
Morphine,  Codeine,  Nar- 

cotine,  .  .  .429 
Strychnine,  Brucine,  So- 

lanine,  Veratrine,    .        430 
Aconitine,    Sanguinarine, 
Theine,  Caffeine,  The- 
obromine,        .         .       431 
OTHER  VEGETABLE  PRINCIPLES. 
Amygdaline,  Asparagine,   432 
Salicine,  Saligenine,  Sali- 

retine,  .  .  .433 
Helicine,  Phloridzine,  434 


Xll 


CONTENTS. 


THE  CYANIDS,  AND  THE  COM- 
POUNDS DERIVED  FROM  THEM. 

Hydrocyanic  Acid,      .        435 
Cyanid  of  Potassium,  .        436 
Cyanogen,  .         .         .        437 
Cyanates,  Cyanate  of  Po- 
tash,       .         .         .        438 
Urea,          .         .         .439 
Sulphocyanates,  Mellon,    440 
Melan,        ...        440 
Results  of  the  Complica- 
tion of  the  Cyanids,       441 
Cyanuric  Acid,  Melanine,441 
Ammeline,  Ammelide,       442 
Complex  Cyanids,  Ferro- 
cyanids,  Yellow  Prus- 
siate  of  Potash,        .        442 
Ferro-cyanic  Acid,  Prus- 
sian Blue,  Ferridcyanid 
of  Potassium,          .        444 
Ferridcyanic  Acid,      .        445 
Platino-cyanids,  .          .        445 
Fulminates,  Fulminate  of 

Mercury,     do.    Silver,  446 
ALCARSINE,  AND  THE  BODIES 
DERIVED  FROM  IT. 
Alcarsine,  Chlorarsine,       447 
Kakodyle,  Alcargene,         448 
URIC   ACID,   AND  THE    PRO- 
DUCTS OF  ITS  DECOMPOSI- 
TION, ....        448 
Allantoine,  Alloxan,  Al- 

loxantine,        .         .        449 
Uramile,  Murexide,  Para- 

banic  Acid,     .         .        450 
Oxaluric  Acid,    .         .        451 
HIPPURIC  ACID,        .         .       451 
Glycocoll,    Gelatine    Su- 
gar, Relations  of  Gly- 
cocoll and  Alcargene,    452 
NUTRITIVE  SUBSTANCES  CON- 
TAINING NITROGEN,     .       452 


rxai 
Vegetable    Albumen,  Fi- 

brine,  Caseine,  &c.        452 
Bread,  Yeast,  Animal  Al- 
bumen, Fibrine,Caseine  453 
Proteine,    .         .         .        454 
Gelatine,  Chondrine,  .        455 
THE  BLOOD. — Red  Globules, 
Hematine,  Arterial  Blood,  456 
Chyle,         .         .         .457 
THE  GASTRIC  JUICE,          .        457 
Pepsine,  the  Saliva,     .        458 
THE  BILE. — Cholesterine,        453 
Choleic    Acid    and    Cho- 

leate  of  Soda,  .         .        458 
THE  URINE,      ...        459 
Calculi,       .         .         .460 
THE  BRAIN  AND  NERVOUS  MAT- 
TER,    ....        460 
Cerebric   and    Oleo-phos- 

phoric  Acids,  .        460 

MILK  AND  BONES,  .  .  460 
Analysis  of  Bones,  .  461 
NUTRITION  OF  PLANTS  AND 
ANIMALS,  .  .  .  462 
The  Food  of  Plants,  .  462 
Cellular  Tissue,.  .  463 
Evolution  of  Oxygen, .  463 
Soils,  Inorganic  Constitu- 
ents of  Plants,  .  463 
Action  of  Humus,  .  464 
Growth  of  Air  Plants,  464 
Fertilizers,  Ammonia,Gu- 

ano,  .         .         .        465 

The  Digestive  Function,  465 
Assimilation  of  Fats,  .  466 
Waste  of  Tissues,  .  466 
Objects  of  Respiration,  467 
Uses  of  Oxygen,  .  467 

Vital  Heat,          .         .       467 
Balance   of  Organic   Na- 
ture,      .         .         .       468 
INDEX,     .         .        .        .471 


FIRST  PRINCIPLES 


OF 


CHEMISTRY, 


PART   I.— PHYSICS. 

INTRODUCTION. 

1.  OUR  knowledge  of  nature  begins  with^experienceJ 
While  this  teaches  us  that  like  causes,  under  similar  cir- 
cumstances, produce  like  effects,  we  also  recognise  as  insepa- 
rable from  our  experience,  the  great  principle  that^cyery  event 
must  have  a  cause.)  Man,  "  as  the  priest  and  interpreter  of 
nature,"*  seeks  to  extend  his  experience  by  experiment. 
Every  experiment  is  byt  a/question  addressed  to  naturc^Jask- 
ing  for  an  increase  of  knowledge ;  and  if  we  question  her 
aright,  we  may  be  sure  of  a  satisfactory  answer. 

2, ^bservation  instructs  us  in  a  knowledge  of  the  external 
forms  of  nature!  and  we  thus  acquire  our  first  impressions  of 
the  various  departments  of  Natural  History.  Our  knowledge 
would,  however,  be  very  limited,  without  a  constant  effort 
(to  extend  our  experience  by  experiment^  The  ancient 
tjfreeks  and  Romans  fwere  learned  and  polished  in  the  intel- 
lectual arts,  and  excelled  in  many  branches  of  human  know- 
ledge.^ Their  ignorance,  however,  of  the  works  of  nature, 
and  t«e  laws  by  which  they  are  regulated,  was  extreme ;  and 


1.  What  is  the  beginning  of  our  knowledge  of  nature?  What 
great  principle  do  we  recognise  in  connection  with  experience  ? 
What  is  an  experiment  ?  2.  What  does  observation  teach  ?  How 
does  it  extend  our  knowledge  ?  What  is  said  of  the  ancients  ? 
Why  did  they  fail  ? 

•"Homo  naturae  minister  et  interpret" — Bacon. 


14  INTRODUCTION. 

this  was  because  |hcy  failed  to  question  her  aright y  because 
they  overlooked  the  true  connection  between  cause  and  etfect. 
The  ancient  philosophy  Abounded  in  plausible  arguments^ 
regarding  those  phenomena  of  nature  which  could  not  fail  to 
arrest  the  attention  of  an  intelligent  people;  but  its  reasonings 
were  based  on  anl  a  priori  assumption  of  a  cause,  and  not 
upon  an  inductive  inquiry  alter  facts  and  their  connections. ) 
It  failed  to  apply  itself(to  the  careful  collection  and  study  or 
facts  in  order  to  science.}  Facts  in  naturc(are  the  expression 
of  the  Divine  willAin  the  government  of  the  physical  world. 
/The  universe  of  matter  is  made  up  of  facts,f  which,  observed, 
TTaced  out,  and  arranged,  lead  us  to  the  knowledge  of  certain 
laws  and  forces  which  proceed  /(directly  from  the  mind  of 
God^  These  are  the  "  laws  of  Suture  :'\>cicnce  is  but  the 
exposition  of  them!  and  of  science  based  upon  such  grounds, 
the  ancient  Philosophy  was  cotnpletcly  ignorant. 

3.  It  is  important  to  distinguish. that  knowledge  /vhich  is 
purely  intellectual  in  its  characters  from  that  whicn  results 
from  observation  and  experience.     Speaking  of  this  subject, 
one  of  the  most  learned  of  living  philosophers  says  :    \£J\ 
clever  man,  shut  up  alone,  and  allowed  unlimited  time,  might 
reason  out  for  himself  all  the  truths  of  mathematics,  by  pro- 
ceeding from  those  simple  notions  of  space  and  number,  of 
which  he  cannot  divest  himself,  withoutceasing  to  think  ;  but 
he  could  never  tell,  by  any  eflbrt  of  reasoning,  what  would 
become  of  a  lump  of  sugar,  if  immersed  in   water,  or  what 
impression   would   be  produced  on  the  eye,  by  mixing  the 
colors  yellow  and  bluc.jf — (Hersckel.)     We  may,  however, 
with   propriety   doubt^whether    there    is    any  knowledge  or 
philosophy  so  purely  intellectual,  or  absolute,  that  it  does  not 
imply  some  previous  recognition  of  physical  facts.^ 

4.  The  physical   philosopher  is  also  of  nccpssity\gn  intel- 
lectual philosopher^    The  observation  of  factsubrms  only  the 
foundation  of  science,Vnd  a  fact  isolated  and  unexplained  has 

(  no  scientific  value.  J  The  knowledge  of  physical  laws  deduced 


Characterize  the  ancient  philosophy.  On  what  was  its  reasoning 
based  ?  How  did  it  fail  ?  What  are  facts  ?  How  do  we  detect  the 
laws  and  forces  of  nature  ?  From  whence  do  these  proceed  ? 
What  is  science  ?  3.  What  convenient  distinction  is  named  ? 
"What  remark  is  quoted  in  illustration  of  this  ?  What  doubt  may 
we  entertain  1  4.  What  is  said  of  the  physical  philosopher  / 
What  of  observation  ?  What  of  an  isolated  fact  ? 


INTRODUCTION.  15 

from  the  study  of  observed  facts  will  enable  the  philosopher 
fro  foretell  the  result  of  the  possible  combination  of  those 
raws'!  and  to  assign  reasons  for  apparent  departures  from 
them.  In  this  way  (discoveries  are  predicted  and  detailed  1 
observation  is  anticipated,  and  called  on  to  verify  the  alleged 
discovery.  The  perturbations  of  the  planet  Uranus  ^ndicated 
the  existence  of  some  body  in  space  heretofore  unknown.," 
yWhen  Le  Verrier  had  reconciled  these  disturbances^Jwith  the 
supposed  influence  of  a  new  planet,  and  determined  its  ele- 
ments of  motion,  he  had  as  truly  discovered  the  remote  sphere 
which  now  bears  his  name,  as  when  the  German  astronomer, 
by  pointing  his  telescope  to  the  precise  place  in  the  heavens 
which  Le  Verrier  had  designated,  announced  to  the  world 
that  the  stupendous  prediction  was  verified  by  observation. 
In  like  manner,  a  familiarity  with  chemical  laws  enables  the 
chemist  to  (foretell  the  result  of  combinations  ^vhich  he  has 
never  investigated,  and  in  some  cases  even  to  assign  the  con- 
stitution of  bodies  which  he  has  never  analyzed. 

5.  Our  knowledge  of  nature  is  conveniently  classified 
kinder  three  great  divisions,!  which  are,  Natural  History, 
Mechanical  Philosophy,  and  Chemistry.  The  first  teaches 
fus  the  characters  and  arrangement  of  the  various  forms  of 
animal  and  vegetable  life  and  minerals,  giving  origin  to  the 
sciences  of  Zoology,  Botany,  and  Mineralogy  J  Mechanical 
Philosophy  (explains  the  laws  which  govern  masses  of 
matter,  without  considering  of  what  that  matter  is  composed./ 
It  tells  us  how  bodies  fall  to  the  earth, — how  liquids  spout 
from  an  orifice ;  it  explains  the  power  of  the  lever,  the  screw, 
and  the  inclined  plane ;  it  teaches  us  the  mechanical  laws 
of  the  atmosphere  and  of  the  celestial  bodies,  the  phenomena 
of  tides  and  currents  and  the  winds ;  but  it  tells  us 
nothing  of  the  nature  of  the  various  substances  of  which  it 
treats. 

I  Chemistry  begins  where  the  natural  sciences  end  J  It  teaches 
us  the  intimate  and  invisible  constitution  of  bodies,  and 
reveals  to  us  the  compounds  which  may  be  formed  by  the 


What  does  a  knowledge  of  natural  laws  enable  the  philosopher  to  do  ? 
What  happens  in  this  way  ?  Illustrate  this  in  case  of  the  perturba- 
tions of  Uranus.  When  had  Le  Verrier  truly  made  his  discovery  ? 
What  can  the  chemist  do  ?  5.  How  is  our  knowledge  of  nature 
classified  ?  What  does  the  first  teach  ?  Mechanical  philosophy 
teaches  what  ?  Define  the  province  of  Chemistry. 


16  MATTER. 

union  of  simple  substances,  and  the  laws  of  their  combination. 
lit  investigates  the  forces  resident  in  matter,}and  which  are 
inseparable  from  our  idea  of  molecular  action, — forces  whose 
play  produces  the  phenomena  of  Light,  of  Heat,  and  of 
Electricity.  Chemistry  also  unfolds  the\wonderful  operations 
of  animal  and  vegetable  life,Jso  far  as  their  functions  dej>cnd 
upon  chemical  laws,  as  in  tne  processes  of  respiration  and 
digestion. 

While  we  now  direct  our  attention  to  Chemistry,  we 
naturally  inquire,UVhat  is  Matter?  ) 

I.  MATTER.  V 
1.   General  Properties  of  Matter. 

G(  Experience  ^founded  on  the  evidence  of  our  senses,  has 
convinced  us  of  the  existence  of  matter.  We  feel  tin* 
resistance  which  it  offers  to  our  touch ;  we  sec  that  it  has 
form,  and  occupies  space,  and  hence  we  say  it  has  extent ; 
and,  lastly,  we  attempt  to  raise  it,  and  we  find  ourselves 
opposed  by  a  certain  force  which  we  call  weight. 

Matter  possesscsfextensionA  Ix'cause  it  occupies  some  space. 
It  islimpenetrablcj  Ix.'causc  one  particle  of  matter  cannot 
occupy  the  same  space  with  another  at  the  same  time.  It 
ha^  gravityjbecausc  it  olx'ys  the  law  of  universal  gravitation. 
Whatever,  therefore,  possesses  these  three  qualities,  is  matter. 

7.  Let  us  look  at  these  qualities  a  little  more  attentively. 
The  largest  and  most  solid  masses  of  matter,  even  entire 
mountains,  may  be  ground  down  by  mechanical  force  to  dust 
so  fine  that  the  winds  will  bear  it  away ;  but  each  minute 
particle  still  occupies  some  space,  and  we  may  imagine  that 
a  great  multitude  of  smaller  particles  may  still  be  formed 
from  its  further  division.  A  grain  of  gold  may  be  spread 
out  so  thin  as  to  cover  600  square  inches  of  surface  on  silver 
wire,  and  an  ounce  can  in  this  manner  be  made  to  cover 
1300  miles  of  such  wire.  One  grain  of  green  vitriol, 

What  is  its  relation  to  the  powers  of  matter  ?  It  also  unfolds  what 
of  life  ?  What  inquiry  naturally  arises  in  commencing  tho  study  of 
Chemistry  ?  G.  What  evidence  have  \ve  of  the  existence  of  matter  ? 
What  three  qualities  are  named  as  belonging  to  matter  ?  What  is 
extension  ?  What  is  impenetrability  ?  What  do  we  mean  by  weight? 
7.  If  we  reduce  solid  matter  to  dust,  do  we  destroy  its  quality  of 
extension  ?  Give  an  illustration  in  the  case  of  gold,  of  the  divisibi- 
lity of  matter. 


GENERAL  PROPERTIES  OF  MATTER.  17 

(sulphate  of  iron)  dissolved,  and  diffused  in  20  million  grains 
of  water,  will  still  be  easily  detected  by  the  proper  tests. 
The  delicate  perfume  of  musk,  which  is  due  to  matter  in  an 
exceedingly  fine  state  of  division,  has  been  known  to  remain 
for  many  years  in  a  drawer  or  apartment,  and  still  to  emit 
very  decided  fragrance.  Of  course  it  had  continued  to  give 
its  appropriate  odor  during  the  whole  time ;  and,  being 
invisible  at  first,  we  may  form  some  idea  of  the  wonderful 
minuteness  of  each  particle. 

The  organic  world  also  presents  us  with  beautiful  exam- 
ples of  the  great  divisibility  of  matter,  in  the  remarkable  forms 
of  animalcules  revealed  by  the  microscope,  many  millions  of 
which  can  be  embraced  in  a  single  drop  of  water.  Yet  each 
of  these  inconceivably  minute  organisms  has  its  own  muscu- 
lar, digestive,  and  circulatory  systems.  How  minute,  then, 
the  ultimate  particles,  of  which  many  myriads  must  be  con- 
tained in  each  animalcule ! 

It  is,  however,  maintained,  that  matter  is  not  infinitely 
divisible ;  for  none  of  the  attributes  of  infinity  can  be  predi- 
cated of  that  which  is  finite. 

8.  Molecules,  or  Atoms. — Every  mass  of  matter,  how- 
ever minute,  is  composed  of  a  vast  number  of  extremely 
minute  particles,  which  we  call  molecules,*  or  atoms.  What- 
ever size  these  particles  may  possess,  they  are  the  centres  of 
all  the  forces  or  powers  whose  united  effect  gives  matter 
all  its  known  properties.  We  can,  however,  form  some  idea 
of  the  relative  size  and  weight  of  these  molecules,  as  is  made 
evident  by  the  laws  of  chemical  combination ;  and  the  laws 
of  crystallization  also  reveal  the  fact  that  they  have  an 
inherent  difference  of  form,  some  being  spherical  while 
others  are  ellipsoidal. 


Give  another  illustration  in  the  case  of  iron.  A  third  case  (the 
perfume)  is  mentioned.  What  illustration  does  the  organic  world  offer  ? 
Is  matter  then  infinitely  divisible  ?  8.  How  is  every  mass  com- 
posed ?  What  is  a  molecule  ?  What  is  said  of  them  ?  What  do 
we  know  of  their  relations  ?  What  further  do  the  laws  of  crystal- 
lization show  ? 

*  Molecule,  a  diminutive,  from  moles,  a  mass.     This  term  is  pre- 
ferable to  '  atom'  or  '  ultimate  particle'  as  implying  no  theory,  which 
both  the  others  do.     Atom  is  from  a  privative  and  temno,  I  cut,  sig- 
nifying their  supposed  indivisibility. 
O  * 


18  MATTER. 

We  know  that  matter  of  all  sorts  is  influenced  by  the  laws 
of  universal  gravitation.  It  is  the  constant  operation  of  this 
law  on  matter  which  gives  it  the  property  that  wo  call 
weight,  which  is  the  measure  of  the  force  required  to  over- 
come the  attraction  of  gravitation.  This  force,  in  the 
language  of  natural  philosophy,  is  said  to  lx?  directly  as  the 
quantity  of  matter,  and  inversely  as  the  square  of  the 
distance.  The  weight  of  a  hody  is  therefore  dependent  on 
the  numt)cr  of  molecules  or  atoms  which  it  contains.  \^ 

9.  Indestructibility  of  Matter. — No   particle  or  aTofti  of 
matter  can  ever  be  annihilated  or  destroyed.     The  same  omni- 
potence which  called  it  into  being  is  required  to  destroy  it. 
But,  it  may  be  asked,  do  we  not  see  matter  daily  perishing 
before  us   in  our  fires,  and  vanishing  in  smoke  and  vapor? 
Its  forms  do  indeed  vanish  from  our  sight,  but  it  is  not  lost ; 
and  we  shall  learn,  when  we  come  to  attend  to  the  beautiful 
phenomena  of  life,  by  how  divine  an  arrangement  the  winds 
and  the  rains  gather  up  their  lost  atoms,  and  restore  them  to 
the  earth,  thus  clothing  it  with  new  beauty. 

10.  Cohesion. — The  power  of  gravitation  just  mentioned, 
acts  alike  on  all  matter,  and  at  all  distances.     Hut  the  power 
which  holds   together  the  several   particles  of  matter  which 
form  a  solid   mass,  acts  on  particles  of  a   like  kind,  and  at 
insensible  distances.     This  attraction  of  aggregation  is  called 
the  force  of  cohesion, — that  power  which  we  must  overcome 
before  we  can   reduce  a  piece  of  marble  or  lead  to  dust  or 
smaller   fragments.       Opposed    to  this   force,   which    would 
draw  together  and  keep  united  all  the  particles  of  a  body,  we 
have  the  power  of  repulsion,  whose  tendency  is  to  separate 
these  particles  from  one  another. 

In  illustration  of  the  first  of  these  powers,  if  we  press  together 
two  smooth  surfaces  of  lead,  clean  and  bright,  as  for  example 
the  halves  of  a  bullet  cut  through,  they  will  adhere  or  unite 
together  so  firmly  as  to  require  the  power  of  several  pounds 
weight  to  draw  them  apart.  The  plates  of  polished  glass, 


What  law  influences  all  matter  ?  What  property  in  bodies  is  due 
to  this  law  ?  On  what  does  the  weight  of  a  body  depend  ?  9.  What 
of  .the  destructibility  of  matter  /  What  becomes  of  the  matter 
burnt  or  turned  into  vapor  ?  Is  it  lost  ?  How  shall  we  prove  this  ? 
10.  What  other  power  of  attraction  is  here  mentioned  ?  How  dif- 
fering from  gravitation  ?  Among  what  particles  exerted  ?  What  is 
it  called  ?  What  opposing  force  have  we  ?  Its  tendency  is  what  ? 
What  example  illustrates  the  attraction  of  aggregation  ? 


GENERAL  PROPERTIES  OP  MATTER.  19 

also,  which  are  prepared  for  large  mirrors,  if  allowed  to 
rest  together,  with  their  surfaces  in  close  contact,  have 
been  known  to  unite  so  firmly  as  to  break  before  they  would 
yield  to  any  effort  to  separate  them.  This  is  owing  to 
the  force  of  attraction  between  the  particles  of  the  same 
kind,  called  homogeneous  attraction,  or  the  attraction  of  ag- 
gregation. 

11.  Repulsion. — We  see  the  second  of  these   opposing 
powers,  namely,  repulsion,  in  one  of  the  common  effects  of 
HEAT.     This  power  is  able  to  overcome  the  strongest  attrac- 
tion, and  to  separate,  to  a  great  distance,  the  particles  before 
closely   united.      Heat  will  convert  ice  into  water,  and  the 
water  into  invisible  vapor.     The  most  solid  metals  cannot 
resist  its  power ;  and  yet,  when  it  ceases  to  operate,  the  an- 
tagonist power  of  attraction  again  draws  the  separated  parti- 
cles together,  and  restores  the^riginal  form. 

12.  Chemical  Attraction. — Matter  is,  however,  governed 
by  another  and  yet  more  powerful  force  of  attraction,  namely, 
the  power  of  affinity,  or  chemical  attraction.     It  is  unlike 
the  power  of  gravity,  because  it  acts  only  at  invisible  dis- 
tances, and  is  also  unlike  the  power  of  cohesion,  (attraction 
of  aggregation,)  because  it  exists  only  between  particles  of 
different  kinds.     Gravity  acts  on  all  matter  and  at  all  dis- 
tances.    Cohesion  acts  only  on  the  same  kind  of  matter  at 
insensible  distances.     Chemical  affinity   acts  only   between 
unlike  particles  at  insensible  distances. 

13.  The  action  of  this  marvellous  power  of  chemical  affi* 
mty,  results  in  producing  from  two  unlike  particles  or  atoms 
of  matter,  a  third  body  having  no  resemblance  in  any  of  its 
properties  to  either  of  the  other  two  constituent  particles.     The 
compound  molecule  of  the  new  body  acts  the  part  of  a  simple 
molecule,  in  its  relation  to  other  bodies.     To  follow  out  all 
the  wonderful  results  of  this  power  of  affinity,  and  make 
ourselves   acquainted   with  all   the  new    bodies    which    are 
formed  under  its  influence,  constitutes  the  proper  business  of 


Another  also  ?  What  other  name  is  there  for  this  sort  of  attrac- 
tion ?  11.  What  does  heat  show  us?  How  does  it  act?  What 
changes  will  it  produce  on  water  ?  If  removed  again,  what  happens  ? 
12.  What  other  force,  still,  governs  matter  ?  Differs  from  gravity 
and  aggregation  in  what  ?  Contrast  these  three  sorts  of  attraction 
by  their  actions.  13.  What  is  the  result  of  chemical  affinity  ?  What 
properties  has  the  third  body? 


20  MATTER. 

the  chemist.     To  do  this,  we  must  first  become  familiar  with 
a  number  of  other  important  subjects. 

14.  Elements. — If  we  could  imagine  a  world  to  exist,  com- 
posed wholly  of  lead  or  of  iron,  and  capable  of  supporting  human 
life,  it  would  afford  no  opportunity  for  the  study  of  the  science 
of  chemistry,  which  owes  its  existence  to  the  fact  that  matter 
is  various  and  not  simple.     We  learn  not  onlv  that  there  are 
different  kinds  of  matter  in  the  world,  but  also  that  nearly  all 
the  forms  in  which  we  see  it  in  nature,  or  in  which  we  make 
it  combine  by  art,  are  capable  of  being  reduced  to  a  few  sim- 
ple substances,  which  are  called  elements.     An  element  is  a 
form  of  matter  which  has  hitherto  resisted  all  attempts  to  ob- 
tain from  it  any  thing  more  simple.     The  numl>cr  of  such 
bodies  at  present  known  is  fifty-six,  and  of  these  all  things  arc 
made.     The  progress  of  science  may  show  us,  by  improved 
methods  of  investigation,  that  jome  of  our  elements  are  com- 
pounds, or,  on  the  other  hand,  some  new  ones  may  be  dis- 
covered.    Water  was  one  of  the  four  elements  of  the  ancients, 
(earth,  air,  fire,  and  water.)     We  now  know  that  water  is  a 
compound  of  two  gaseous  elements,  (oxygen  and  hydrogen.) 
Gold  is  an  example  of  what  we  suppose  to  l>e  an  clement. 
We  can  alter  its  form  by  combining  it  with  other  substances, 
thus  making  it  part  of  a  new  compound,  but  no  process  has 
ever  enabled  us  to  show  that  it  is  itself  a  compound.     The 
process    by  which    a    body  is    shown   to  be   compound,   i.s 
called  analysis  ;  and  that  by  which  the  same  body  is  repro- 
duced, by  the  direct  union  of  its  elements,  is  called  synthesis. 
Where  these  two  modes  of  proof  arc  united,  the  evidence 
obtained  is  of  the  very  highest  kind. 

15.  Imponderable  Agents. — Besides  the  elementary  mat- 
ter of  the  world  of  which  we  have  already  spoken,  there 
are  certain  other   agents  of  so  subtle  a   nature   that   they 
possess  none  of  the  common  properties  of  matter.     These 
are  Light,  Heat,  and  Electricity ;   they  are  frequently  called 


14.  What  if  the  world  were  made  of  iron  or  lead  ?  To  what  docs 
chemistry  owe  its  existence  ?  What  do  we  learn  of  matter  ?  Arc 
things  about  us  generally  simple  or  compound  ?  In  what  sense  is 
the  term  element  used  in  chemistry  ?  Do  we  positively  *now  any 
element  ?  What  illustration  is  named  of  the  elements  of  the  an- 
cients ?  What  is  cold  ?  How  can  we  alter  its  properties  ?  What 
is  analysis  ?  What  synthesis  ?  What  is  the  best  kind  of  proof  in 
chemistry  ?  15.  What  other  agents  are  there  besides  those  already 
mentioned  ?  What  have  they  been  called  ? 


THE    THREE    STATES    OF    MATTER.  21 

imponderable  agents,  because  we  have  never  been  able  to 
collect  and  weigh  them.  Of  their  real  nature,  it  must  be 
remembered,  we  know  nothing.  We  shall  treat  of  them  as  if 
they  were  matter,  because  the  language  of  science  accords 
with  this  mode  of  presenting  their  phenomena.  Late  investi- 
gations countenance  the  opinion  that  they  are  inseparably 
connected  with  the  existence  of  matter,  and  should  be  classed 
philosophically  with  its  general  powers  or  forces.  Chemical 
affinity  has  been  considered  identical  with  electricity.  It  is 
also  considered  as  an  established  fact  in  science,  that  there 
exists,  throughout  all  space,  an  extremely  rare  elastic  medium, 
called  ether,  whose  vibrations  cause  the  phenomena  of  light. 
Whatever  may  be  the  ultimate  fate  of  this  opinion,  it  is  found 
to  accord  with  the  most  mathematical  exactness  with  all  the 
phenomena  of  optics.  ., 

2.   The  Three  States  fy  Matter — the  Solid,  Fluid,  and 
Gaseous* 

10.  The  three  common  conditions,  or  states,  in  which 
matter  is  known  to  us,  are  the  solid,  fluid,  and  gaseous.  In- 
deed we  may  reduce  them  simply  to  solids  and  fluids,  if  we 
choose  to  consider  fluids  as  of  two  sorts,  elastic  fluids,  as  air 
and  vapor,  and  inelastic  fluids,  as  water  and  other  liquids. 
We  have  already  hinted  that  these  several  states  of  matter 
depend  on  the  power  of  heat.  (11.)  This  cause  will  be  more 
fully  considered  in  the  chapter  on  heat. 

17.  Properties  of  Solids. — It  is  the  distinguishing  property 
of  solids  to  have  their  particles  bound  together  by  so  strong 
an  attraction  as  in  a  great  measure  to  destroy  their  power  of 
moving  among  each  other. 

No  solid,  however,  not  even  gold  and  platinum,  which  are 
the  most  compact  solids  known,  has  its  particles  of  matter 
so  aggregated  as  to  be  incapable  of  some  condensation. 
Blows,  pressure,  or  a  reduction  of  temperature,  will  condense 
almost  all  solids  into  a  smaller  bulk,  and  water  may  even  be 


What  of  the  nature  of  these  ?  What  have  we  reason  to  believe  ? 
What  is  said  of  a  pervading  ether  ?  16.  Name  the  three  states  of 
matter.  Reduce  them  to  two.  Distinguish  between  the  two  classes 
of  fluids,  and  give  an  example.  What  cause  is  suggested  for  these 
different  states  of  bodies  ?  17.  What  is  said  to  be  the  distinguish- 
ing feature  of  solids?  What  is  said  of  the  most  compact  bodies? 
How  can  they  be  diminished  in  bulk? 


22  MATTER. 

forced  through  the  pores  of  gold,  by  very  great  mechanical 
pressure.  AH  solid  bodies  are,  therefore,  considered  as 
porous,  and  their  particles  are  believed  to  touch  each  other  in 
comparatively  few  points. 

18.  Solids  possess  several  other  properties  which  may  bo 
considered  in  one  way  or  another  as   modifications  of  the 
power  of  cohesion.  (10.)     (1.)  Hardness  ;  this  property  is 
possessed  by  solids  in  very  various  degrees,  from  the  diamond, 
the  hardest  of  all  substances,  to  those  solids  which  are  so  soft 
as  to  be  easily  scratched  by  the  finger-nail,  as  lead  and  some 
minerals.     Hardness  has  no  connection  with  weight  or  densi- 
ty, for  lead  is  more  than  three  times  as  heavy  as  the  diamond. 
(2.)  Elasticity  ;  or  the  power  of  assuming  their  original  form 
after  being  bent  or  compressed.     It  is  found  in  all  degrees  of 
perfection,  from  glass  and  steel,  which  are  almost  perfectly 
clastic,  to  lead,  which  possesses  none  of  this  quality.   (U.) 
Brittleness  is  often  closely  connected  with  the  last  property. 
If  glass  or  steel  be  bent  beyond  a  certain  degree,  it  breaks 
suddenly:  this  point  is  the  limit  of  their  elasticity.  (4.)  Mal- 
leability, or  the  capability  of  being  beaten  by  blows  into  thin 
leaves,  is  found  in  thn  highest  perfection  in  gold,  and  in  a 
good  degree  in  many  other  metals  ;  300,000  leaves  of  gold 
are  but  an  in  h  thick  ;  while  an  equal  number  of  leaves  of 
common  letter  paper  would  be  several  rods  in  thickness.  (5.) 
Ductility  and   laminability  are  properties  closely  allied  to 
malleability.     Iron,  for  instance,   unless   heated,  cannot  be 
beaten  like  gold,  but  it  may  be  drawn  into  fine  iron  wire  (duc- 
tility) and  plated  by  rollers  into  thin  sheets,  (laminability.) 

19.  Fluids. — Fluids  arc  distinguished  from  solids  by  tho 
perfect  freedom  of  motion  among  their  particles.     We  havo 
said  (16)  that  fluids  may  be  divided  into  two  classes;  liquids, 
like  water,  and  gases  or  vapors,  like  air  and  steam.     The 
first  is  inelastic,  or  very  nearly  so;  the  second  highly  elastic. 
We  will  consider  them  separately. 

20.  Liquids  press  with  equal  force  on  all  parts  of  a  vessel 


What  proof  of  the  porousness  of  gold  ?  What  of  solids  in  general  ? 
18.  Of  what  force  are  the  several  properties  connected  in  this  sec- 
tion modifications  ?  Enumerate  these  properties.  What  is  hard- 
ness ?  Give  an  example.  Is  it  connected  with  weight  or  density  ? 
(2)  What  is  elasticity  ?  (3)  Brittleness  ?  (I)  Malleability  ?  Give 
an  example  and  a  comparison.  (.">)  How  do  ductility  and  laminabi- 
lity differ  from  malleability  ?  19.  Distinguish  fluids  from  solids. 
Classify  them.  (16.)  20.  How  do  liquids  press  on  a  containing  vessel? 


THE    THREE    STATES    OF    MATTER.  23 

containing  them.  If  an  attempt  be  made  to  condense  water, 
for  instance,  in  a  tight  vessel,  the  pressure  exerted  for  this 
purpose  will  at  once  be  felt  in  every  part  of  the  fluid,  and  on 
all  sides  of  the  containing  vessel  to  the  same  degree  as  on  the 
portion  where  the  power  is  applied.  Liquids  are  said  to  be 
inelastic ;  but  this  is  not  strictly  true,  for  water  may  be  com- 
pressed, in  the  reft^d  apparatus  of  CErsted,  one  part  in 
22,000  for  every  atmosphere  of  pressure,  and  the  water  in  a 
vessel  sunk  to  the  depth  of  1000  fathoms  (6000  feet)  in  the 
sea,  has  been  compressed  to  nineteen-twentieths  of  its  origi- 
nal bulk.  For  all  practical  purposes,  however,  water  and 
other  fluids  are  inelastic,  so  that  they  may  be  applied  to  exert 
immense  power  in  the  hydrostatic  press. 

21.  Capillary  attraction  is  a  property  possessed  by  fluids 
as  distinguished  from  solids.  By  this  property,  fluids  will 
mount  in  small  tubes  (called  capillary  or  hair  tubes,  from 
the  hairlike  fineness  of  the  bore)  to  a  considerable  height 
against  the  power  of  gravity.  It  is  this  power  which  enables 
wood  and  other  porous  bodies  to  draw  up  into  their  pores  any 
fluid  with  which  they  may  come  in  contact.  Water  standing 
in  a  tumbler  has  its  surface  made  concave,  being  raised  by 
capillary  attraction  at  the  edges  where  it  comes  into  contact 
with  the  glass. 

The  capillary  force  is  so  great,  that  plugs  of  dry  wood 
driven  into  holes  bored  for  the  purpose,  in  rocks,  and  then 
saturated  with  water,  swell  so  much  from  the  quantity  of 
water  drawn  into  the  pores  of  the  wood,  (by  capillary  attrac- 
tion) as  to  burst  open  the  rocks.  By  the  same  power,  a  lamp 
or  candle  draws  up  its  supply  of  fuel.  A  solid  bar  of  lead, 
bent  like  the  letter  U,  and  one  end  of  it  put  into  a  vessel  of 
quicksilver,  (the  only  metal  which  is  a  fluid  at  common 
temperatures,)  after  some  time  becomes  so  saturated  with 
the  mercury  by  capillary  action,  as  to  convey  it  out  of  the 
vessel,  like  a  syphon. 

When  surfaces  are  wet  by  water  or  oil,  or  any  other  fluid, 
it  is  by  virtue  of  this  power ;  and  we  see  from  this  that  the 
capillary  power  is  closely  connected  with  chemical  affinity, 

Give  an  illustration.  What  is  said  of  the  elasticity  of  liquids  ? 
What  of  that  of  water  ?  How  may  they  be  considered,  however  ? 
21.  What  is  capillarity  ?  Define  the  word.  How  is  the  power 
seen  in  a  tumbler  of  water  ?  Also  in  lamps  and  candles  ?  Give  an 
illustration  of  this  power  in  wood.  What  experiment  is  mentioned 
with  lead  ?  What  is  said  of  the  wetting  of  surfaces  ? 


24  MATTER. 

(or  heterogeneous  attraction.)  Mercury,  for  instance,  will 
not  wet  or  cover  the  surface  of  glass  or  the  skin,  nor  of  iron ; 
but  it  at  once  wets  lead,  tin,  gold,  silver,  and  many  other 
metals.  Glass  can  be  wet  by  water  only  with  some  difficulty  : 
oil,  however,  easily  wets  glass,  and  after  this,  water  cannot 
be  made  to  adhere  to  its  surface  at  all. 

22.  The  cohesion  of  the  particles  of  a   liquid   for  each 
other,  is  well   shown  by  the  globular  form  of  the  dew-drop : 
the  power  of  cohesion,  (or  homogeneous  attraction)   tending 
to  bring  all  the  particles  to  a  centre,  produces  a  sphere.     A 
soap-bubble  is  a  beautiful  example  of  the  cohesive  power  of  a 
thin  film  of  liquid.     Soap-water  is  more  viscid,  but  not  more 
coherent  than  pure  water,  and  the  bubble  may  l>o  considered 
as  a  large  drop  of  water,  with  all   its   interior  removed,  and 
the  place  supplied   with   air.     The  cohesive   power  of  the 
particles  of  water  in  the  film  of  the   bubble  is  so  great,  that 
if  the  pipe  be  taken  from  the  mouth  before  the  bubble  leaves 
it,  a  stream  of  air  will  be  driven  forcibly  from^hc  bore  of  the 
pipe,  by  the  contraction  of  the  film.  ^^ 

23.  Elastic  fluids  are  either  gases  or  vapbrs.     A  gas  is 
matter   in  a  pertnancnf.li/  aerial    form.     A  vapor  is   matter 
temporarily   in  an  aerial   form.     The  same   physical   laws 
govern  both,  and  we  will  briefly  review  thorn. 

24.  The  Atmosphere  and  Laws  of  Gases. — We  live  on 
this  planet  at  the  bottom  of  a  vast  ocean  of  gaseous  matter, 
which  we  call   the  air,  or  our  atmosphere.     It  surrounds  us 
everywhere,  and  presses  upon  us  with  a  weight  which,  when 
stated  in  numbers,  seems  beyond  belief.     Under  its  influence, 
all  operations,  chemical  as  well  as  mechanical,  arc  performed. 
It  penetrates  deeply   into  the  crust  of  the  earth   itself,  and  is 
largely  dissolved  in  all  its  waters.     Its  chemical   composition 
will  be  discussed  in  its  proper  place,  when  we  come  to  con- 
sider the  properties  of  the  two  elements  of  which  it  is  princi- 
pally composed. 


How  is  it  connected  with  capillarity  ?  Give  an  illustration  in 
mercury,  and  in  oil  and  water  on  glass.  22.  How  is  the  power  of 
cohesion  shown  in  liquids  ?  What  is  said  of  the  soap-bubble  ? 
How  may  we  consider  th«.>  bubble  /  What  is  said  of  the  cohesive 
powor  of  the  film?  IIo'.v  is  this  weil  illustrated?  23.  What  are 
elastic  fluids?  (16  and  19.)  Define  a  ea=.  Define  a  vapor.  24.  To 
\vhat  is  the  air  compared  ?  Wiiat  i«  said  of  it  ?  Is  it  confined  to  the 
surface  ? 


THE  ATMOSPHERE. 


25 


25.  It  is  usual   to  speak  of  a  vessel  or  apartment   which 
contains  air  only,  as  empty.     It  is  easy  to  show,  however, 
that  the  so-called  empty  space  is  in  reality  full,  and  that  the 
matter  it  contains  is  just  as  capable  of  being  weighed,  trans- 
ferred, and  rendered  sensible  by  its  resistance  to  other  bodies, 
as  any  other  form  of  matter.     If  we  plunge  a  bell-glass  or 
inverted  tumbler  into  water,  holding  its  mouth   horizontally 
downwards,  we  shall   find  a  resistance  to  its  descent,  which 
arises  from  the  air  confined  within  it.     The  water  will  rise  in 
the  vessel  to  a  certain  height,  which  varies  with  the  degree 
of  pressure  we  apply.     The  deeper  we  sink  the  glass,  the 
higher  will  the  water  rise  in  its  interior,  and  the   less   space 
will  the  air  occupy :  as  we  diminish  the  pressure,  the  air,  by 
its  elasticity,  returns  to  its  former  dimensions,  and  entirely 
displaces  the  water. 

26.  Elasticity  of  the   Air. — Suppose   the  two  tight-bot- 
tomed hollow  cylinders  a  and  6,  in  the  annexed  figure,  to  be 
filled  with  air:  if  we  fit  a  plug  so 

tightly  to  the  sides  of  both,  that  no 
air  can  pass  between  it  and  the  sides 
of  the  cylinder,  and  then  try  to  force 
down  this  plug  by  pressure  on  the  , 
stem,  we  shall  find  a  resistance  to 
its  downward  motion.  The  plug, 
or  piston  as  it  is  called,  descends 
indeed,  but  with  increasing  resistance 
as  it  goes  down  ;  and  if  the  pressure 
be  removed,  it  returns  to  its  former 
position,  suddenly  and  with  force. 
We  have  thus  demonstrated  not  only 
that  the  air  is  a  material  substance, 
offering  resistance,  but  also,  that  it  is 
an  elastic  substance,  capable  of  compression  to  an  indefinite 
extent,  and  of  restoration  to  its  former  condition  on  the  with- 
drawal of  the  pressure. 

27.  The  elasticity  of  the  air  may  also  be  shown  by  placing 
the  piston  in  &,  in  the  position  represented  in  the  drawing,  the 
air  beneath  it   being  in  the  same  state  of  pressure  as  that 


What  is  said  of  a  so-called  empty  vessel  ?     How  can  we  illus- 
trate the  presence  of  air  in  an  empty  vessel  '/    26.  Explain  the 
mode  by  which  the  elasticity  of  the  air  is  shown  in  this  section. 
27.  How  is  its  elasticity  shown  in  the  cylinder  b  (26)  ? 
3 


26 


MATTER. 


above ;  if  we  now  attempt  to  raise  the  piston,  the  air  which 
before  filled  only  one-half  of  the  cylinder,  will  expand  and 
fill  the  whole ;  and  this  would  be  the  case,  if  at  the  com- 
mencement of  the  experiment  only  one-thousandth  part  of  the 
vessel  contained  air.  The  tension  of  the  expanded  portion, 
as  it  is  termed,  would  then  be  only  one-thousandth  part  of 
ordinary  air  at  the  earth's  surface.  We  thus  learn  that  air, 
and  also  many  other  gases,  are  perfectly  elastic  ;  although, 
as  we  shall  see  further  on,  there  are  a  number  of  gases 
which  can,  by  great  cold  and  pressure,  be  reduced  to  liquids, 
and  some  of  them  even  to  a  solid  form. 

28.  Air-Pump. — The  remarks  just  made  serve  also  to  ex- 
plain the  principle  and  construction  of  the  common  air-pump, 
an  instrument  of  great  importance  to  science.  In  order  to 
make  an  air-pump  of  one  of  the  cylinders  already  described, 

it  is  necessary  only  to  open 
a  communication  in  the 
bottom  of  the  cylinder, 
with  some  vessel  from 
which  we  wish  to  remove 
the  air,  and  also  to  open  a 
hole  in  the  piston  commu- 
nicating with  the  external 
air.  Each  of  the  holes  is 
covered  with  a  little  flap 
or  lid  of  leather  or  oiled 
silk,  fitting  the  orifice  close- 
ly, and  called  a  valve. 
Both  these  valves  open 
freely  in  an  upward  direc- 
tion, but  the  lower  one  is 
tightly  closed  by  the  least  downward  pressure.  In  the  an- 
nexed figure  this  arrangement  is  shown.  We  have  a  glass 
vessel,  (called  an  air-receiver,)  from  which  we  wish  to  re- 
move the  air.  The  receiver  is  made  to  fit  tightly  by  its  edges 
on  the  metallic  plate,  from  which  passes  a  tube  forming  a 
connection  with  the  bottom  of  the  cylinder,  where,  as  shown 
in  the  above  figure,  the  lower  valve  is  placed.  Suppose  the 

How  does  half  the  air  fill  all  the  space  ?  To  what  extent  will  this 
occur  ?  What  term  expresses  the  degree  of  elasticity  ?  28.  What 
important  instrument  do  the  foregoing  principles  explain  ?  How 
may  one  of  the  cylinders  a  or  b  (26)  be  made  into  an  air-pump? 
Explain  the  construction  and  use  of  the  same  in  the  figure. 


THE  ATMOSPHERE.  27 

piston  to  be  in  the  place  shown  in  the  figure,  and  that  we 
attempt  to  raise  it  by  the  rod :  as  it  rises,  the  air  beneath  it 
expands,  to  fill  the  enlarged  space,  and  with  it  the  air  in  the 
glass  vessel  and  tube  also  expands,  while  the  little  valve  at  the 
bottom  allows  the  air  to  pass  freely  into  the  cylinder  from 
the  glass,  to  supply  the  vacancy  occasioned  by  the  rise  of 
the  piston.  If  we  now  press  the  piston  down,  the  air  beneath 
in  the  cylinder  cannot  return  into  the  receiver  by  the  lower 
valve  which  opens  only  upward,  and,  with  the  least  downward 
pressure,  closes  the  opening  tight ;  but  the  valve  in  the  piston 
itself  now  opens  outwardly,  the  air  beneath  passes  out  and 
escapes,  while  the  piston  descends  freely  to  the  bottom  of 
the  cylinder.  We  may  now  raise  it  again,  when  a  fresh  por- 
tion of  air  will  come  in  from  the  glass  vessel,  and  be  again 
expelled  through  the  piston-valve,  when  the  piston  is  again 
pushed  downwards.  By  continuing  this  process,  we  pump 
out  the  greater  part  of  the  air,  as  with  a  common  pump  we 
draw  water  from  a  well.  We  cannot,  however,  remove  all 
the  air  in  this  way,  because,  as  just  explained,  the  smallest 
quantity  of  air  will  expand  so  as  to  fill  the  entire  space. 
This  process  is  called  exhaustion. 

29.  Vacuum. — The  space  thus  produced   by  exhausting 
the  air  is  called  a  vacuum,  or  empty  space ;  a  perfect  va- 
cuum, however,  cannot  be  formed  in  this  way,  although  the 
air-pump  can  produce  an  exhaustion  which  answers  all  the 
purposes  of  science  and  art.     Many  forms  of  the  air-pump 
are  in  use,  all,  however,  depending  upon  the  principles  ex- 
plained.     One  of  the  most  common  is  that  in  which  two 
pistons  are  so  arranged  (see  fig.  in  26)  as  to  work  up  and 
down  alternately,  being  moved  by  a  winch  and  toothed  wheel. 
Sometimes  the  cylinders  are  formed  of  heavy  glass  tubes, 
which  enable  the  student  to  see  the  manner  in  which  the  pis- 
ton and  valves  move,  and  better  to  understand  the  operation. 
The  air-pump  depends  entirely  on  the  elasticity  of  the  air  for 
its  successful  operation. 

30.  Law  of  Mariotte. — The  volume  or  bulk  of  air  at  a 
given  temperature,  depends  on  the  pressure  to  which  it  is 
subject,  or,  in  other  words,  the  volume  of  the  air  is  always 


What  raises  the  valves  ?  On  pressing  the  piston  down,  why  does 
not  the  air  return  ?  How  does  the  air  beneath  it  escape  ?  What  is 
the  process  compared  to  ?  What  is  it  called  ?  29.  What  is  tha 
empty  space  called  ?  Why  cannot  a  perfect  vacuum  be  formed  ? 


28 


MATTER. 


1 


inversely  as  the  pressure,  while  the  density  is  directly  as 
the  pressure.  This  is  called  the  law  of  Mariottc,  who  was 
the  first  accurately  to  demonstrate  it  by  ex- 
periments. The  annexed  figure  shows  the 
simple  apparatus  used  by  him  for  this  pur- 
pose. It  is  a  glass  tube  turned  up  and  scaled 
at  the  lower  end  :  a  graduated  scale  of  equal 
parts  is  attached  to  it.  Mercury  is  poured 
into  the  open  end  of  this  tube  so  as  to  rise; 
just  to  the  first  horizontal  line,  and  a  portion 
of  air  of  the  ordinary  elasticity  is  thus^en- 
closed  in  the  short  limb  of  9  inches.  Now 
if  mercury  be  poured  into  the  longer  leg,  so 
that  it  may  stand  at  30  inches  (33)  above 
the  level  of  the  mercury  in  the  snorter  leg, 
it  will  press  with  its  whole  weight  on  the 
included  air,  which  will  then  1x3  found  to 
occupy  4£  inches,  only  half  of  its  former 
space.  If,  iu  like  manner,  the  column  of 
mercury  1x3  increased  to  twice  this  length, 
its  pressure  on  the  included  air  will  be  tri- 
pled, and  the  space  occupied  by  it  will  be 
reduced  to  one-third,  and  so  on  in  simple 
proportion. 

31.  Weight  of  the  Atmosphere. — It  has 
been  abundantly  shown  by  the  experiments 
already  explained  that  the  air  has  weight. 
The  first  movement  of  the  air-pump  will  fix  the 
air-glass  on  the  plate  ofthr  pump,  and  after 
a  tolerable  exhaustion  is  produced,  great 
force  will  be  required  to  remove  the  jar,  and 
the  pump  itself  may  often  be  lifted  by  it. 
The  power  that  holds  the  air-jar  down  is 
only  the  weight  of  the  air  pressing  upon  the 
upper  side  of  the  glass,  while  that  pressure 
is  removed  from  the  inside  of  the  glass,  by 
the  action  of  the  pump;  an  upward  pressure 
is  also  exerted  upon  the  under  side  of  the 
board  or  plate  of  the  pump,  thus  co-operating  with  the  down- 


30.  What  is  meant  by  the  volume  of  air  ?  On  what  does  it  de- 
pend ?  State  the  law  in  precise  terms.  What  is  this  law  called  ? 
Explain  the  apparatus  which  illustrates  it.  31.  How  do  we  know 
that  air  has  weight  ? 


THE  ATMOSPHERE.  29 

ward  pressure  upon  the  glass  receiver.  The  leather  by  which 
boys  raise  large  stones  and  bricks,  acts  in  the  same  way.  The 
leather  adheres  to  the  stone  only  because  the  air  is  pressed 
out  from  the  surfaces  of  contact,  and  rests  with  all  its  weight 
on  the  upper  side.  The  difficulty  which  we  experience  in 
raising  our  feet  from  a  wet  clay  soil,  is  due  in  a  degree  to 
the  same  cause ;  and  if  the  air  could  be  perfectly  removed 
from  beneath  our  feet,  we  should  be  as  firmly  and  immoveably 
planted  on  the  earth  as  a  well- rooted  tree. 

The  weight  of  the  air  is  also  well  shown  by  the  burst- 
ing of  a  piece  of  bladder-skin  tied  tightly  over  the  mouth 
of  an  open  jar  on  the  plate  of  the  air-pump. 
As  the  purnp  is  worked,  the  flat  surface  of  the 
bladder  becomes  more  and  more  concave,  and  at 
length  bursts  inward  with  a  smart  explosion.  The 
same  accident  would  befall  the  glass  jars  used  on 
the  air-pump,  if  they  were  not  made  of  strong 
glass,  and  arched  in  form.  Thin  square  glass  bottles  are 
blown  purposely  to  show  this,  and  burst  under  the  air-pump, 
being  either  crushed  inward  by  removing  the  air,  or  bursting 
outward  by  the  expansion  of  the  contained  air,  when  they  are 
surrounded  by  a  vacuum.  J^ 

32.  We  can  also  determine  the  weight  of  the  air  by  ex- 
hausting a  small  glass  globe  fitted  by  a  stop-cock  to  the  pump. 
Suppose  such  a  globe  to  hold   100  cubic  inches  of  air  at  the 
medium  temperature  and  pressure  :  if  we  weigh  it  before  and 
after  exhaustion,  we  shall  find,  if  the  vacuum  be  perfect,  that 
it  has  lost  nearly  31   grains  of  weight,  which  it  regains  on 
allowing  the  air  to  enter;    hence  we  learn  that  100  cubic 
inches  of  air  weigh  about  31  grains.     By  using  other  gases 
besides  air,  we  ascertain  by  a  similar  experiment  their  rela- 
tive weights  and  specific  gravities,  (49,  and  figure  in  the 
same  section.) 

33.  Barometer. — The  Barometer*  is  an  instrument  by 
which,  on  principles  just  explained,  we  actually  measure  the 

What  force  holds  down  the  receiver  of  the  pump  ?  Explain  the 
action  of  the  leather  "  sucker."  Why  is  it  difficult  to  raise  our  feet 
in  wet  clay  ?  Give  another  experimental  illustration  of  the  weight 
of  the  air.  32.  How  may  we  illustrate  its  weight  accurately? 
How  much  do  100  cubic  inches  weigh  ?  33.  What  is  the  barome- 
ter ?  Give  its  definition. 

*  From  the  Greek,  la^os,  weight,  and  wietron,  measure. 
3* 


30  MATTER. 

weight  of  the  atmosphere.  This  instrument  was  invented 
A.  D.  1643,  by  a  celebrated  Italian  philosopher,  named  Torri- 
celli.  Philosophers  up  to  this  time,  when  called  to  explain  the 
phenomena  of  the  atmosphere  and  the  rise  of  water  in 
a  common  pump,  had  contented  themselves  with  sav- 
ing that  "  Nature  abhors  a  vacuum ;"  but  a  well- 
digger  in  Florence  informed  Torricelli,  that  he  could 
raise  water  in  a  pump  only  33  feet,  and  this  philoso- 
pher at  once  reasoned,  that  if  nature  abhorred  a  va- 
cuum, there  was  no  reason  why  she  should  cease  to 
abhor  it  when  it  was  more  than  33  fat  high.  He  in- 
ferred that  this  column  of  water  must  be  equal  in  weight 
to  the  entire  height  of  an  atmospheric  column  of  equal 
size.  To  prove  this  experimentally,  it  was  only 
necessary  to  use  a  fluid  so  much  heavier  than  water, 
as  to  bring  the  height  of  the  column  down  to  con- 
venient dimensions.  Mercury,  which  is  13£  times 
heavier  than  water,  was  the  fluid  selected.  A  strong 
glass  tube  about  3  (bet  long,  sealed  at  one  end,  was 
filled  with  mercury.  The  finger  being  placed  on 
the  open  end  as  a  stopper,  the  tube  was  inverted, 
and  the  mouth  immersed  in  a  small  vessel  of  mer- 
cury. On  withdrawing  the  finger,  the  mercury  in 
the  tube  sank  a  certain  distance,  oscillated  up  and 
down,  and  finally  came  to  rest  nt  the  height  of  about 
30  inches  from  the  surface  of  the  mercury  in  the 
outer  vessel.  The  empty  space  atxjve  the  mercury  is 
the  most  perfect  vacuum  that  can  be  produced,  and  is 
called  the  Torricellian  vacuum,  in  honor  of  the 
discoverer  of  the  barometer.  If  water  were  em- 
ployed instead  of  mercury,  it  would  require  a  tube 
about  33  feet  long. 
34.  Determination  of  the  Pressure  of  the  Atmosphere. — 
Water  and  mercury  are  supported  at  these  respective 


Who  discovered  it,  and  when  ?  What  explanation  has  been  be- 
fore given  of  atmospheric  pressure  ?  What  observation  did  the 
well-digger  of  Florence  make?  How  did  Torricelli  explain  it? 
What  simple  experiment  did  he  choose,  to  prove  his  inference  ?  Ex- 
plain the  arrangement  of  apparatus  in  the  figure.  What  happened  in 
withdrawing  the  finger  ?  At  about  what  height  will  the  vibrating 
column  of  mercury  stand  ?  What  is  the  space  above  the  mercury 
called  ?  If  water  were  used,  how  long  a  tube  would  be  required  ?  31. 
What  sustains  the  mercury  or  \vator,  the  tube  being  open  at  bottom? 


THE    THREE    STATES    OF    MATTER.  31 

heights  by  the  weight  or  pressure  of  the  air  on  the  surface  of 
the  fluid.  Such  a  column  of  mercury  becomes  thus  an  exact 
counterpoise  for  the  weight  of  the  atmosphere.  If  the  tube 
had  the  area  of  one  inch  exactly,  and  the  mercury  in  the 
barometer  tube  stood  at  30  inches,  we  should  find  that 
fifteen  pounds  of  mercury  would  be  required  to  fill  ihe  tube. 
The  pressure  of  the  air,  then,  on  the  surface  of  the  mercury, 
is  capable  of  supporting  a  column  of  that  metal  weighing  fifteen 
pounds.  This  is  also  the  weight  of  a  column  of  air  of  the 
same  size,  reaching  to  the  supposed  limits  of  the  atmosphere. 
Every  square  inch  of  the  surface  of  land  or  sea  is  therefore 
subject  to  a  pressure  equal  to  fifteen  pounds,  or  to  a  column  of 
mercury  30  inches  in  height.  A  man  of  ordinary  size  has  a 
surface  of  about  15  square  feet,  and  he  must  consequently 
sustain  a  pressure  on  his  body  of  about  15  tons.  This  pro- 
digious load  he  bears  about  with  him  unconsciously,  because 
the  mobility  of  the  particles  of  air  causes  it  to  bear  with  equal 
force  on  every  part  of  his  body,  beneath  his  feet  as  well  as 
on  his  head,  and  in  the  inner  cavities  as  well  as  on  the 
outer  surface ;  if  it  were  not  so,  great  inconvenience  and  even 
death  must  result.  We  can  easily  feel  the  pressure  of  the 
atmosphere  on  our  own  persons,  by  placing  one  of  our  hands 
over  the  mouth  of  an  air-jar,  as  is  seen  in  the  annexed  figure, 
when  a  single  stroke  of  the.  pump  will 
firmly  fix  the  hand,  which  seems  drawn  in 
by  what  we  are  accustomed  to  call  suction, 
but  which  we  now  see  to  be  only  the 
external  pressure  of  the  atmosphere.  On 
letting  the  air  in  again,  we  cease  to  feel 
this  sensation,  because  the  balance  or  equi- 
librium of  pressure  is  restored. 

35.  The  pressure  of  the  air  at  the  surface  is  not  a  constant 
quantity.  This  is  shown  by  the  barometer,  the  mercury  in 
which  will  be  found  to  vary  in  height  at  different  times  as 
much  as  2  or  2|.  inches  between  one  extreme  and  another. 
This  variation  arises  from  the  fact,  that  the  quantity  of  air 

How  much  mercury  is  a  counterpoise  to  the  atmosphere,  and  in  how 
long  a  tube,  of  what  diameter  ?  Whence  we  infer  what  about  the 
pressure  on  the  surface  of  every  thing  ?  A  man  sustains  what  load 
of  air  ?  Why  are  we  unconscious  of  this,  and  why  does  it  not  crush 
us  ?  We  can  convince  ourselves  of  the  reality  of  this  by  what  sim- 
ple experiment?  What  is  meant  by  what  we  commonly  call 
section  ? 


32  MATTER. 

varies  from  time  to  time  at  the  same  places,  owing  to  meteo- 
rological causes  which  this  is  not  the  place  to  discuss ;  but 
hence  arises  the  value  of  the  barometer  as  a  weather-glass, 
and  to  show  with  precision  the  amount  of  atmospheric  pressure 
at  any  given  time.  The  barometer  is  also  of  great  use  in 
measuring  the  heights  of  mountains;  because  it  will  be  seen 
from  what  has  been  already  said,  that  the  air  at  the  level  of 
the  sea  must  weigh  more  than  on  a  high  hill,  since  the 
former  is  pressed  down  by  and  supports  the  weight  of  the 
entire  atmosphere,  while  on  the  mountain  top  we  have  risen 
above  a  certain  portion  of  the  entire  weight  of  the  air.  The 
air  grows  more  and  more  rare  as  we  ascend,  and  the  ba- 
rometer falls  in  exact  proportion.  The  inconvenience  which 
travellers  have  experienced  in  ascending  high  mountains  has, 
it  is  said  on  good  authority,  been  very  much  exaggerated. 
The  heart  continues  its  action  under  a  diminished  external 
pressure,  and  no  serious  consequences,  it  is  believed,  ever 
follow,  as  the  bursting  of  blood-vessels  or  lesion  of  the  lungs, 
as  some  have  asserted.  On  the  summit  of  Chimborazo, 
Baron  von  Humboldt  found  that  his  barometer  had  sunk  to 
13  inches  11  lines,  and  the  same  philosopher  descended  into 
the  sea  in  a  diving-bell,  until  the  mercurial  column  rose  to  45 
inches  ;  he  consequently  has  safely  experienced  a  change  of 
31  inches  of  pressure  in  his  own  person. 

Limits  of  the  Atmosphere. — A  person  who  has  risen  in 
a  balloon,  or  on  a  mountain,  to  the  height  of  2*705  miles, 
or  14,282  feet,  has  passed  through  one-half  of  the  entire 
weight  of  the  air,  and  finds  his  barometer  to  indicate 
this  by  standing  at  15  inches.  The  upper  limits  of  the 
atmosphere  cannot  be  accurately  determined,  but  it  is  sup- 
posed from  the  observations  of  astronomers  to  be  about  45 
miles  high.  We  may  judge,  then,  how  extremely  thin  or 
rare  the  upper  portions  must  be,  when  we  have  one-half  of 


35.  Is  the  pressure  of  the  air  constantly  the  same  ?  How  does 
the  barometer  show  this?  It  varies  how  much?  Arising  from 
what  cause  ?  What  common  name  for  the  barometer  is  derived  from 
its  use?  What  other  important  use  is  made  of  the  barometer? 
Whence  its  use  for  this  purpose?  What  observations  did  Hum- 
boldt make  on  Chimborazo?  What  depth  did  he  reach  in  the  sea? 
How  many  inches  of  pressure  has  he  personally  experienced  ?  How 
high  must  one  ascend  in  order  to  pass  through  half  the  weight  of  the 
air?  Where  will  his  barometer  then  stand"  How  high  is  the  atmo 
sphere  believed  to  extend? 


WEIGHT    AND   SPECIFIC    GRAVITY.  33 

its  entire  weight  within  less  than  three  miles  of  the  earth's 
surface. 

3.   Weight  and  Specific  Gravity. 

36.  At  every  step  of  research  the  chemist  must  appeal  to 
his  balances.  This  instrument  should  possess  a  beam,  in- 
flexible by  the  weight  intended  to  be  used,  and  should  be 
delicately  poised  on  a  sharp  edge  of  hardened  steel,  (called 
the  knife-edge,)  resting  on  a  plate  of  agate,  mounted  on  the 
summit  of  an  upright  pillar  of  brass.  The  beam  should  be 
so  accurately  made  that  it  will  assume  a  horizontal  position 
when  at  rest,  its  index  or  pointer  marking  zero,  on  the  small 
scale  near  the  foot  of  the  column.  At  each  end  of  the  beam  is 
also  a  knife-edge  supporting  the  scale-pan,  and  in  a  delicate 
balance  there  is  always  an  adjustment  by  which,  when  the 
instrument  is  not  in  use,  the  beam  is  supported  on  points  inde- 
pendent of  the 
delicate  knife- 
edge,  which 
is  thus  saved 
from  unneces- 
sary wear. — 
A  good  ba- 
lance will  turn 
readily  with  a 

weight  of  one- 

thousandth  part  of  a  grain,  when  each  arm  supports  'one 
thousand  grains.  In  delicate  weighing,  a  glass  case  is  em- 
ployed to  protect  the  balance  from  the  fluctuations  of  the 
atmosphere.  When  accurate  results  are  required  with  a 
balance  whose  arms  are  of  unequal  length,  or  which  is  from 
any  cause  inaccurate,  the  method  adopted  is  to  weigh  the 
substance  accurately  in  each  pan,  and  to  take  the  mean  of 
the  two  weighings,  which  will  give  the  true  weight ;  or  the 
substance  being  placed  in  one  pan,  is  counterpoised  accu- 
rately by  the  addition  of  shot  or  bits  of  foil  in  the  other :  it 
is  then  removed,  and  its  place  supplied  with  known  weights 
till  the  equilibrium  is  restored.  The  weights  added  give  the 
weight  of  the  substance.  The  above  figure  shows  the  form 


What  do  we  infer  of  its  rarity  in  the  upper  regions  ?  36.  To 
what  instrument  does  the  chemist  constantly  appeal  ?  Explain  the 
construction  of  the  balance.  Its  use. 


34-  MATTER. 

of  a  good  balance,  arranged  for  taking  specific  gravities. 
One  pan  is  removed,  and  a  shorter  one  (b)  substituted,  from 
which  by  a  silk  thread  the  substance  (a)  is  supported  in  a 
glass  of  pure  water,  as  explained  in  41. 

It  is  always  assumed,  when  the  weights  of  substances  arc 
stated  in  books  of  science,  that  the  operation  was  performed 
at  a  given  temperature  by  the  thermometer;  and  60°  of 
Fahrenheit's  scale  is  the  point  agreed  upon,  because  that  is 
about  the  usual  temperature  of  the  air;  and  if  it  be  higher  or 
lower,  a  corresponding  allowance  is  made,  because  the  bulk, 
and  consequently  the  specific  weight  of  bodies,  differ  with 
their  temperature.  This  precaution  is  necessary  only  when 
we  take  the  sj>ecific  gravity  of  bodies,  and  not  their  absolute 
weights. 

37.  Density. — The  density  of  a  body  is  a  direct  result  of 
the  law  of  gravity  as  already    explained    (8),    the    weight 
of  a  body  being  the  measure  of  the  force  of  gravity,  which 
is    directly    proportioned    to    the    quantity    of  matter.     The 
greater  the  number  of  particles  of  a  given  kind  within  a  given 
space,  the  greater  the  density  of  the  body,  or  in  the  language 
of  common   life,   the  henrier  it    is.     Now   as   bodies   differ 
greatly  in  this  particular,  each  body  is  said  to  have  a  specific 
gravity,  or  density,  j>eculiar  to  itself. 

38.  Specif  c  Gravity. — The  specific  gravity  of  a  body  is 
its  weight,  compared  with  that  of  some  other  body  of  exactly 
equal  volume.     We  say  that  lead  is  heavier  thnn  cork  ;  by 
which  we  mean,  that  of  equally  sized  pieces  of  these  sub- 
stances, one  is  very  many  times  heavier  than  the  other;  that 
is,  there  is  very  much  more  matter  in  the  one  than  in  the  other 
under  equal  dimensions.     As  a  difference  in  s|>ecific   gravity 
in  bodies  is  found  to  be  accompanied  by  other  important  dif- 
ferences, we  will  give  an  account  of  the  methods  of  deter- 
mining this  character  in  liquids,  solids,  and  in  gases. 

39.  Standards  of  Specific  Gravity. — Pure  water    at    a 
temperature  of  60°  is  the  substance  which  has  been  adopted 
as  a  standard  of  comparison  for  the  specific  gravity  of  all 
solid    and    liquid    substances ;     while   the    dry   atmospheric 


37.  What  is  density?  What  law  is  it  the  result  of?  (8.)  The 
density  of  a  body,  then,  is  the  measure  of  what  force?  What  is  the 
density  peculiar  to  each  sort  of  matter  called  ?  38.  Define  Specific 
Gravity.  What  is  meant  when  we  say  that  one  body  is  heavier  than 
another?  What  is  said  of  the  importance  of  specific  gravity?  39. 
Name  the  standard  adopted  for  comparison  of  specific  gravity? 


WEIGHT    AND    SPECIFIC^  GRAVITY. 


35 


air  at  60°  of  Fahrenheit  and  30  inches  of  the  barometer  is 
the  standard  assumed  for  all  gases  and  vapors.  Thus  calling 
water  1,  lead  will  be  1 1-445,  or  lead  is  nearly  eleven  and  a  half 
times  as  heavy  as  water.  Cork  is  lighter  than  water,  and 
must  be  expressed  by  a  fractional  number.  Oil  of  vitriol 
(sulphuric  acid)  has  a  specific  gravity  of  1-847  when  p'ure, 
or  nearly  twice  as  much  as  water.  A  pint  measure  of  this 
dense  liquid  would  weigh  nearly  twice  as  much  as  a  similar 
measure  of  water ;  while  a  pint  of  quicksilver  would  weigh 
thirteen  and  a  half  times  as  much  as  a  pint  of  water,  and  a 
like  measure  of  alcohol  only  about  three-quarters  as  much, 
(0-794  being  the  specific  gravity  of  alcohol.)  We  see  now 
the  necessity  of  knowing  accurately  the  temperature  of 
substances  compared,  at  the  time  of  weighing,  as  their  bulk 
increases  materially  with  every  increase  of  temperature,  and 
their  specific  gravity  consequently  diminishes. 

40.  Specific  Gravity  of  Liquids. — To  measure  the  spe- 
cific gravity  of  liquids  accurately,  a  small  thin  glass  bottle 
is  required,  which  holds  a  known  weight  of  pure  water  at 
60°  when  accurately  filled.  One  thousand  grains  is  a  con- 
venient quantity  for  comparison ;  but  a  smaller  quantity  is 
often  more  convenient,  when  we  have  but  little  of  a  substance, 
although  it  then  requires  a  simple  calculation  to  reduce  it  to 
the  standard.  The  accompanying  figure  a  shows  such  a 
bottle.  To  its  neck  a  glass  stopper  is 
adapted,  by  grinding,  which  is  perfo- 
rated by  a  small  hole. 
The  weight  of  the  bot- 
tle is  counterpoised  by 
a  small  mass  of  lead, 
which  is  easily  cut  by 
a  knife  to  the  exact 
weight.  This  coun- 
terpoise is  carefully 
preserved  for  this  pur- 
~V  pose.  The  bottle  is 
now  ready  for  use ;  it  is  filled  with  the 
fluid  under  examination,  the  stopper  is 
carefully  introduced,  and  the  excess  of  the  liquid  gushes  out 


Of  solids  and  fluids.  Also  for  gases  and  vapors.  Mention  the  ex- 
amples given  in  the  text.  40.  Explain  the  method  of  finding  the 
specific  gravity  of  fluids,  and  the  apparatus  figured  in  this  section. 


36  % MATTER. 

through  the  small  orifice.  The  exterior  of  the  bottle  is  wiped 
dry,  and  its  weight,  when  thus  filled,  is  ascertained ;  and  if 
the  bottle  is  graduated  to  1000  grains  of  pure  water  at  60°, 
the  weight  obtained  is  the  specific  gravity.  For  instance,  if 
the  fluid  is  pure  ether,  the  1000  gr.  bottle,  when  filled,  would 
weigh  only  720  grains,  and  '720  is  the  specific  gravity  of 
ether.  As,  however,  it  may  not  be  always  convenient  to 
procure  a  thousand-grain  bottle,  any  glass  phial  may  be 
converted  into  one,  which  will  answer  the  piirjx>se  very  well. 
Suppose  it  to  contain  376  grains  of  pure  water:  then,  as 
376  :  1000,  so  is  the  weight  obtained  to  the  specific  gravity 
of  the  fluid.  A  little  bottle  like  the  annexed  cut  (ft)  answers 
the  same  purpose,  although  in  a  less  accurate  manner  than 
that  with  the  perforated  stopper.  Its  neck  is  quho  narrow,  v 
and  the  lines  marked  on  it  show  the  upper  and  lower  surfaces  / 
of  the  liquid  in  the  neck.  The  quantity  of  pure  water  whicrw"" 
it  holds  at  this  point  is  learned  from  previous  trial. 

41.  Specific  Gravity  of  Solids. — The  dctermi  nation  <9i*" 
the  specific  gravity  of  solids  is  founded  on  the  theorem  first 
proved  by  Archimedes,  that  irhen  a  solid  body  is  immersed 
in  water,  it  loses  a  portion  of  its  weight  exactly  equal  to 
the  weight  of  the  tratcr  displaced.  The 
story  in  which  it  is  stated  that  this  philosopher 
detected  the  fraud  of  King  Micro's  goldsmith, 
in  furnishing  to  the  monarch,  as  a  crown  of 
pure  gold,  one  made  of  a  debased  metal,  is 
a  good  example  of  the  practical  value  of  this 
theorem.  In  fact,  plunging  an  irregular  solid 
into  water,  is  the  only  mode  by  which  we  can 
easily  and  accurately  measure  the  precise  bulk 
of  the  body  as  compared  with  an  equal  bulk  of 
water.  For  convenience  in  taking  the  specific 
gravities  of  solids,  a  small  scale-pan  is  hung  to 
one  arm  of  the  balance,  (as  shown  in  36,) 
and  the  instrument  brought  to  a  |>erfect  equi- 
librium. A  hook  is  attached  to  the  lower  sur- 
face of  this  pan,  for  suspending  a  thread.  It  is 
required  to  take  the  specific  gravity  of  the  mineral  quartz. 

If  the  bottle  holds  more  than  1000  grains,  what  course  is  adopted  ? 
41.  On  what  is  the  method  for  the  specific  gravity  of  solids  founded  ? 
State  this  theorem  in  precise  terms.  What  anecdote  is  mentioned 
of  Archimedes  ?  How  do  we  proceed  in  taking  the  specific  gravity 
of  a  solid  ?  Why  does  the  specimen  weigh  less  in  water  ? 


WEIGHT    AND    SPECIFIC    GRAVITY.  37 

The  specimen  is  attached  by  a  filament  of  raw  silk,  or  a  fine 
hair,  with  a  noose  at  the  end,  to  the  hook,  and  the  actual 
weight  of  the  mass  hanging  in  the  air  accurately  determined. 
But,  in  order  to  have  its  weight  as  compared  with  water, 
we  must  know  precisely  how  much  a  mass  of  water  will 
weigh,  which  is  just  equal  in  bulk  to  the  specimen.  Now  if 
we  suspend  it  as  it  hangs  from  the  scale-beam  in  a  vessel  of 
pure  water,  we  shall  displace  just  such  a  quantity  of  water 
as  corresponds  with  the  bulk  of  the  crystals,  and  no  more  ; 
the  water  will  buoy  up  the  specimen  by  a  weight  just  equal 
to  a  like  bulk  of  water  :  in  other  words,  the  specimen  will 
weigh  less  in  water  than  it  did  in  air  ;  and  we  must  diminish 
the  weight  on  the  other  side  of  the  beam,  to  correspond  with 
this  loss  of  weight.  If  we  now  subtract  from  the  weight  in 
air,  that  which  we  have  found  to  be  its  weight  in  water,  the 
difference  will  evidently  give  us  the  weight  of  a  bulk  of  water 
exactly  equal  to  the  bulk  of  our  specimen.  As  water  is 
the  standard  of  comparison  which  has  been  adopted  for  spe- 
cific gravity,  if  we  divide  the  actual  weight  of  the  substance 
in  air  by  the  weight  of  an  equal  bulk  of  water,  we  shall  have 
the  specific  gravity  sought. 

42.  We  deduce  the  following  rule  for  determining  specific 
gravity.  Subtract  the  weight  in  water  from  the  weight  in 
air,  divide  the  weight  in  air  by  the  difference  thus  found, 
and  the  quotient  will  be  the  specific  gravity.  A  single 
example  may  serve  to  impress  this  simple  but  important 
subject  on  the  mind  of  the  learner  :  we  find  on  trial  that  the 

Weight  of  the  substance  in  air,  is  357-95  grs. 

Weight  of  the  substance  in  water,        "  239-41    " 

Difference,      .....         118-54    « 
sli  =  3'01  8Pecific  gravity.* 


How  much  less  does  it  weigh  ?  42.  State  the  rule  which  is  given 
for  finding  the  specific  gravity.  Give  an  example  on  the  black-board. 
(Note.)  Explain  the  principles  and  use  of  Nicholson's  Araeometer. 
Give  an  example  of  its  use. 


*  Nicholson's  Arceometer. — A  cheap  and  convenient  substitute  for 
the  balance  is  found  in  a  little  instrument  represented  in  the  annexed 
cut,  and  called  Nicholson's  Arceometer,  which  we  will  briefly  de- 
scribe, v  is  a  metallic  ball  or  float  having  a  descending  hook,  to 
which  is  hung  a  little  weighted  pan  I  to  hold  the  substance  which  is 
4 


38 


MATTER. 


43.  Substances  which  are  lighter  than  water  can  have 
their  specific  gravity  taken,  by  attaching  to  them  any  con- 
venient bit  of  metal  which  will  sink  them ;  the  weight  of  the 
substance  is  taken  in  air,  and  then  the  united  weight,  after 
attaching  the  piece  of  metal.     The  weight  in  water  of  both 
united  is  now  taken,  and  the  light   body  being  detached,  the 
weighing  is  repeated  on  the  metallic  body. 

44.  For  this   purpose  we  may  also  take  some  liquid  in 
which  the  light  body  will  just  float,  and  then  determine  the 
specific  gravity  of  the  fluid  by  the  bottle,  (40,)  which  will  give 
us  at  once  the  specific  gravity  of  the  solid.     Thus,  if  we  put 
a  lump  of  wax  into  water,  it  will  float  above  the  surface;  but 

43.  How  can  we  take  the  specific  gravity  of  substances  lighter 
than  water  ?  44.  Explain  another  method  by  the  use  of  the  speci- 
fic gravity  bottle,  and  its  principle. 


weighed  in  water  ;  the  wire  stem  /  supports  a  cup  c. 
A  mark  t  on  the  stem  shows  the  point  at  which  the 
whole  apparatus  will  float  in  a  tall  vessel  of  water 
when  a  certain  known  weight  (called  the  balance 
weight)  is  put  in  the  cup  r.  The  specimen  under 
examination  must  not  exceed  in  weight  the  balance- 
weight,  this  being  the  limit  of  the  instrument.  Sup- 
pose the  limit  to  be  100  grains.  To  find  by  this  in- 
strument the  specific  gravity  of  a  substance,  place  it 
on  c,  and  add  weights  till  the  instrument  sinks  to  the 
mark  t ;  the  added  weight  being  subtracted  from 
100,  gives  the  weight  of  the  specimen  in  air.  Now 
place  the  specimen  in  the  pan  /,  and  again  add 
weights  to  c.  As  much  more  weight  on  c  will  now 
be  required  as  corresponds  to  the  weight  of  a  bulk 
•  of  water  equal  to  the  specimen,  which  it  must  be 

remembered  is  buoyed  up  by  a  power  just  equal  to  such  weight. 

The   difference  of  weight  thus  found  will    be    the    divisor    of  the 

weight  of  the  specimen,  and  the  quotient  will  be  the  specific  gravity 

sought. 

This  instrument  is  generally  made  of  brass  or  tin-plate,  but  may 

be  more  elegantly  made  of  glass. 

For  example,  put  the  specimen  in 

Balance  weight  =  100-00 

Weights  added  to  sink  instrument  to  t  =     22-57  grs. 

Weight  of  specimen  in  air  =  77-43 

Specimen  placed  in  lower  pan  requires  ad- 
ditional weights  =  35-43 

77'  43 
35.43 — 22-57=  12-86,  the  weight  of  a  like  bulk  of  water  ;  then  ^^ 

=  6-02,  the  specific  gravity  sought. 


WEIGHT    AND    SPECIFIC    GRAVITY.  39 

in  pure  alcohol  it  will  sink.  If  we  dilute  the  alcohol  by  small 
doses  of  water,  we  shall  soon  find  a  point  when  the  wax  will 
just  float,  or  rise  and  sink  indifferently.  The  alcohol  at  this 
state  of  dilution  has  the  same  specific  gravity  as  the  wax,  and 
this  we  find  by  the  specific  gravity  bottle  to  be  about  0-9. 

45.  If  a  substance  is  in  powder  or  in  small  grains,  its 
specific  gravity  is  found  by  taking  a  known  weight  of  it,  and 
having  introduced  it  into  the  specific  gravity  bottle  for  fluids, 
to  fill  it  with  pure  water  and  weigh  :  the  weight  of  the  sub- 
stance being  deducted  from  the  weight  of  the  whole  contents 
of  the  bottle,  the  difference  between  the  sum  thus  obtained 
and  the  weight  of  the  water  which  the  bottle  alone  will  hold, 
corresponds  with  the  difference  between  the  weight  of  the  sub- 
stance in  air  and  water.  For  instance,  we  introduce  100 
grains  of  a  powdered  mineral  into  a  specific  gravity  bottle, 
holding  1000  grains  of  pure  water,  and  fill  the  remaining 
space  with  water  at  60°.  We  might  expect  that  we  should 
have  a  weight  of  1100  grains,  but  find  only  1059,  the  place 
of  some  of  the  water  being  occupied  by  the  powder  introduced. 

The  bottle  holds,  1000  grains. 

Substance  introduced  weighs,  100       " 

1100 
Weight  found,  1059 


Difference,  41 

100 

~4l  =  2-044,  the  specific  gravity  sought. 

46.  If  the  substance  is  soluble  in  water,  we  must  employ 
a  fluid  of  known  specific  gravity,  in  which  it  is  not  soluble. 
For  instance,  sugar  cannot  be  weighed  in  water,  but  in  abso- 
lute or  pure  alcohol    it  can.      The  specific  gravity   being 
determined  in  a  fluid   whose  specific  gravity,  as  compared 
with  water,  is  known,  it  is  easy  by  a  simple  proportion  to  tell 
the  specific  gravity  of  the  solid. 

47.  The  Hydrometer*  is  an  instrument  of  great  use  in 
determining  the  specific  gravity  of  liquids  without  a  balance. 

45.  If  the  substance  is  in  powder,  how  do  we  proceed  ?  Give  the 
example  named  in  the  text  on  the  black-board.  46.  If  the  sub- 
stance is  soluble  in  water,  how  do  we  proceed  ?  47.  What  is  the 
hydrometer  ? 

*  From  the  Greek  hudor,  water,  and  mctron,  measure. 


MATTER. 


It  is  simply  a  glass  tube  with  a  bulb  blown  on  one  end  of  it, 
containing  a  few  shot  to  counterbalance  the  instrument,  while 
a  scale  of  equal  parts  is  made  of  paper  and  introduced  into 
the  open  end,  which  is  then  tightly  sealed.  This  scale  indi- 
cates the  points  to  which  the  stem  sinks  when  immersed  in 
fluids  of  different  densities.  The  fluid  for  convenience  is 
placed  in  a  tube  or  narrow  jar ;  the  more  dense  the  fluid,  the 
less  quantity  will  the  hydrometer  displace,  while  in  a  lighter 
fluid  it  will  sink  deeper.  The  zero  point  of  the  scale  is 
always  placed  where  the  instrument  will  rest  in  pure  water, 
after  which  the  graduation  is  effected  on  a  variety  of  arbi- 
trary scales,  all  of  which  can  however  be  referred  to  the  true 
specific  gravity,  by  calculation.  The 
scales  of  these  instruments  read  either  up 
or  down,  according  as  the  fluid  to  be 
measured  is  either  heavier  or  lighter  than 
water.  In  case  of  alcohol,  (it  being  lighter 
than  water,)  the  graduation  of  the  hy- 
drometer is  made  to  indicate  the  number 
of  parts  of  pure  alcohol  in  a  hundred 
parts  of  the  liquid,  absolute  alcohol  being 
100,  and  water  0.  The  hydrometers  of 
Baume  (a  French  maker)  are  much  used 
in  the  arts.  These  instruments  are  of  the 
greatest  service  to  the  manufacturer,  and 
when  carefully  made  are  sufficiently  ac- 
curate for  most  purposes  of  the  laboratory. 
They  should  always  be  proved  by  comparison  with  the 
balance  before  they  are  accepted  as  standards.  For  many 
purposes  they  are  made  of  brass  or  ivory,  as  well  as  of  glass. 
48.  Little  balloons  or  bulbs  of  glass  are  frequently  em- 
ployed to  find,  in  a  rough  way,  the  density  of 
fluids.  When  several  of  them  are  thrown  in  a 
fluid  of  known  density,  some  will  sink,  some  rise 
even  with  the  surface,  and  others  will  just  float. 
Those  which  just  float  are  taken,  and  being  marked, 
(as  in  the  figure,  with  the  density  of  the  liquid 


Explain  its  principal  use.  What  is  the  zero  of  its  scale  ?  In  case  of 
alcohol  how  is  it  graduated  ?  How  do  we  find  the  true  specific  gravity 
from  the  arbitrary  scale  ?  -18.  What  are  specific  gravity  bulbs  ? 
How  are  they  used  ?  Mention  the  case  in  which  they  are  most 
useful. 


SOURCES  AND  PROPERTIES  OF  LIGHT.  41 

which  they  represent,)  are  then  used  to  determine  the  spe- 
cific gravity  of  liquids  of  unknown  density.  They  are  called 
specific  gravity  bulbs,  and  are  of  great  service  in  ascertaining 
the  density  of  gases  reduced  to  a  liquid  by  pressure  in  glass 
tubes,  when,  from  the  circumstances  of  the  experiment,  all 
the  usual  modes  of  ascertaining  specific  gravity  are  inappli- 
cable. The  method  described  in  44  for  finding  the  gravity 
of  light  substances,  involves  the  same  principle  as  that  here 
given. 

49.  Specific  Gravity  of  Gases. — It  remains  only,  under 
this  head,  to  speak  of  the  modes   used   for  determining  the 
specific  gravity  of  gases  and   vapors.     For  this  purpose  a 
globe,  or  other  conveniently   formed   glass  vessel,  holding  a 
known  quantity  by  measure,  (usually   100  cubic  inches)  is 
carefully   freed  from  air  or  moisture,   by  the  air-pump  or 
exhausting  syringe,  and  is  then  filled  with   the  gas 

or  vapor  in  question,  and  at  60°  Fahrenheit,  and 
30  inches  of  the  barometer,  (32),  and  weighed  ;  the 
weight  of  the  apparatus  filled  with  common  air 
being  previously  known,  the  difference  enables  the 
experimenter  to  make  a  direct  comparison.  The  an- 
nexed figure  shows  an  apparatus  for  this  purpose ; 
the  globe  (b)  is  provided  with  a  stop-cock,  (e),  and 
fitted  by  a  screw  to  the  air-jar  (a.)  The  jar  is 
graduated  so  that  the  quantity  of  air  or  other  gas 
entering  may  be  known  from  the  rise  of  the  water 
in  (a.)  It  is  thus  found  that  100  cubic  inches  of 
pure  dry  air  weigh  31-0117  grains,  while  the  same 
quantity  of  hydrogen  gas  weighs  only  2*14  grains, 
being  about  fourteen  times  lighter  than  air. 

II.  LIGHT. 

50.  The  physical   phenomena  of  light  properly  belong  to 
the  science  of  Optics,  a  branch   of  natural  philosophy  not 
necessarily  connected   with    chemistry.      A    knowledge    of 
some  of  the  laws  of  light  is,  however,  required  of  the  chemi- 
cal student,  and  the  progress  of  discovery  daily  shows  us 


What  previous  case  involves  the  principle  of  the  bulbs  ?  49.  How 
do  we  find  the  specific  gravity  of  gases  ?  Explain  the  apparatus 
used.  How  much  do  we  thus  find  the  air  to  weigh  ?  50.  To  what 
branch  of  science  does  light  properly  belong  ?  What  is  said  of  its 
chemical  importance  ? 
4* 


42  LIGHT. 

some  new  connection   between   the  phenomena  of  light  and 
chemical  action. 

51.  Sources  and  Nature  of  Light. — The  sun  is  the  great 
source  of  light,  although  we  can  show  many  minor  and  arti- 
ficial sources.     Of  the  real  nature  of  light  we  know  nothing. 
Sir  Isaac  Newton  argued  that  it  was  a  material  emanation 
from  the  sun  and  other  luminous  bodies,  consisting  of  parti- 
cles so  attenuated  as  to  be  wholly  imponderable  to  our  means 
of  estimating  weight,  and  having  the  greatest   imaginable  re- 
pulsion to  each  other.     These  particles,  by  his  theory,  are 
supposed  to  be  sent  forth  in  straight   lines,  in  all  directions, 
from  every  luminous  body,  and  which,  falling  on  the  delicate 
nerves  of  the  eye,  produce  the  sense  of  vision.     This  is 
called  the  Newtonian  or  corpuscular  theory  of  light.     It  is 
not  now  generally  believed  to  1x3  true,  but  the   language  of 
optical  science  is  formed  on  the  supposition  of  its  correctness. 
The  other  view  or  theory  of  light,  which   is   now  generally 
accepted,   is  called  the   wave   or   undulatory   theory.     It   is 
known  that  sound  is  conveyed  through  the  air  by  a  series  of 
vibrations  or   waves,   pulsating   regularly   in   all    directions, 
from  the  original  source  of  the  sound.     In   the  same  manner 
it  is  believed  that  light  is  conveyed  to  the  eye  by  a  series  of 
unending  and   inconceivably  rapid  pulsations  or  undulations, 
imparted  from  the  source  of  light  to  a  very  rare  or  attenuated 
medium,  which  is  supposed   to  fill   all   space.     This  medium 
is  called   the  luminiferous  ether  (15.)     However  difficult  it 
may  be  to  form  any  just  comprehension  of  the   ultimate  or 
real  nature  of  light,  we  do  know   many  things  about   its 
properties,  some  of  which   may  be  enumerated,  and  briefly 
explained. 

52.  Properties  of  light. — 1st.  Light  is  sent  forth  in  rays 
in  all  directions  from  all  luminous  bodies.     2d.  Italics  not 
themselves  luminous  become  visible  by  the  light  falling  on 
them  from  other  luminous  bodies.     3d/ The  light  which  pro- 
ceeds from  all  bodies  has  the  color  of  the  body  from  which 
it  comes,  although  the  sun  sends  forth  only  white  light.     4th. 


51.  Name  the  great  source  of  light  ?  What  do  we  know  of  its 
nature  ?  Give  the  theory  of  Newton.  What  is  this  theory  com- 
monly called?  What  is  said  of  its  probability  and  truth?  What 
is  the  now  accepted  doctrine  ?  Explain  what  is  meant  by  the  un- 
dulatory theory.  What  is  it  which  is  supposed  to  undulate  ?  What 
name  is  given  to  this  medium  ?  52.  State  what  is  known  of  light. 
1st.  Its  rays.  2d.  Of  its  luminousnoss.  3d.  Of  its  color. 


REFLECTION.  4-3 

Light  consists  of  separate  parts  independent  of  each  other. 
5th.  Rays  of  light  proceed  in  straight  lines.  6th.  Light 
moves  with  a  wonderful  velocity,  which  has  been  computed  by 
astronomical  observations  to  be  at  least  one  hundred  and 
ninety-five  thousands  of  miles  in  a  second  of  time.  This 
velocity  is  so  wonderful  as  to  surpass  our  comprehension. 
Herschel  says  of  it,  that  a  wink  of  the  eye,  or  a  single  motion 
of  the  leg  of  a  swift  runner,  or  flap  of  the  wing  of  the  swiftest 
bird,  occupies  more  time  than  the  passage  of  a  ray  of  light 
around  the  globe.  A  cannon-ball  at  its  utmost  speed  would 
require  at  least  seventeen  years  to  reach  the  sun,  while  light 
comes  over  the  same  distance  in  about  eight  minutes. 

53.  When  a  ray  of  light  falls  on  the  surface  of  any  body, 
several  things  may  happen.     1st.  It  may  be  absorbed  and 
disappear  altogether,  as  is  the  case  when  it  falls  on  a  black 
and  dull  surface.  2d.  It  may  be  nearly  all  reflected,  as  from 
some   polished    surfaces.     3d.  It   may   pass  through    or  be 
transmitted ;  and  4th.  It  may  be  partly  absorbed,  partly  re- 
flected, and  partly  transmitted.     Bodies  are  said  to  be  opake 
when  they  intercept  all  light,  and  transparent  when  they  per- 
mit it  to  pass  through  them.     But  probably  no  body  is  either 
perfectly  opake  or  transparent,  and  we  see  these  properties  in 
every   possible    degree   of    difference.     Metals,    which    are 
among   the  most  opake   bodies,  become   partly  transparent 
when  made  very  thin,  as  may  be  seen  in  gold-leaf  09  glass, 
which  transmits  a  greenish  purple  light,  and  in  quicksilver, 
which  gives  by  transmitted  light  a  blue  color  slightly  tinged 
with  purple.     To  protect  pictures  formed  by  the  daguerreo- 
type process,  they  are  covered  with  a  film  of  gold  or  copper, 
so  thin  as  not  to  injure  the  impression,  and  yet  it  effectually 
prevents  its  removal  by  the  touch.     On  the  other  hand,  glass 
and  all  other  transparent  bodies  stop  the  progress  of  more  or 
less  light. 

54.  Refection. — Light  is  reflected   according   to   a  very 

4th.  Of  its  parts.  5th.  Of  its  course.  6th.  Of  its  velocity.  Il- 
lustrate this  by  the  examples  named  by  Herschel.  What  is  said 
of  the  speed  of  a  cannon-ball  ?  53.  State  what  becomes  of  a  ray 
of  light  falling  on  any  surface.  1st.  On  a  dull  surface.  2d.  On  a 
polished  surface.  3d.  On  a  transparent.  4th.  What  else  may  hap- 
pen ?  What  is  a  transparent  body  ?  What  is  an  opake  one?  Are 
these  qualities  ever  perfect  ?  What  is  said  of  the  opacity  of  gold 
and  quicksilver  ?  Of  the  gold  and  copper  in  the  daguerreotype  ? 
f>4.  State  the  law  of  reflection. 


44 


LIGHT. 


simple  law.  In  the  annexed  figure,  if  the  ray  of  light  fall 
from  P'  to  P,  it  is  thrown  directly 
back  to  P' ;  for  this  reason  a  per- 
son looking  into  a  common  mirror, 
^  sees  himself  correctly,  but  his  im- 
age appears  to  be  as  far  behind  the 
mirror  as  he  is  in  front  of  it.  If 
the  ray  fall  from  R  to  P,  it  will  be 
reflected  to  R',  and  if  from  r,  then  it  will  go  in  the  line  r',  and 
so  for  any  other  point.  If  we  measure  the  angles  R  P  P'  and 
P'  P  R',  we  shall  find  them  equal  to  each  other,  and  so  also 
the  angles  r  P  P'  and  P'  P  r'.  These  angles  arc  called  re- 
spectively the  angles  of  incidence  and  refection.  We  there- 
fore state  that  the  angle  of  incidence  is  equal  to  the  angle 
of  reflection,  which  is  the  law  of  simple  reflection.  This 
law  is  as  true  of  curved  surfaces  as  it  is  of  planes ;  for  a 
curved  surface  (like  a  concave  metallic  mirror)  is  considered 
as  made  up  of  an  infinite  number  of  small  planes. 
"  55.  Simple  Refraction. — If  a  ray  of  light  falls  perpendi- 
cularly on  any  transparent  or  uncrystallized  surface,  ns  glass 
or  water,  it  is  partly  reflected,  partly  scattered  in  all  direc- 
tions, (which  part  renders  the  object  visible,)  and  partly 
transmitted  in  the  same  direction  from  which  it  comes.  If, 
however,  the  light  come  in  any  other  than  a  perpendicular  or 
vertical  direction,  as  from  R  to  A, 
on  the  surface  of  a  thick  slip  of 
glass,  as  represented  in  the  figure, 
it  will  not  pass  the  glass  in  the  line 
R  A  B,  but  will  be  bent  or  refract- 
ed at  A,  to  C.  As  it  leaves  the 
glass  at  C,  it  again  travels  in  a  di- 
rection parallel  to  R  A,  its  first 
course.  Refraction,  then,  is  the 
change  of  direction  which  a  ray 
of  light  suffers  on  passing  from  a 
rarer  to  a  denser  medium,  and  the  reverse.  In  passing  from 
a  rarer  to  a  denser  medium,  (as  from  air  to  glass  or  water,) 


Draw  the  diagram  on  the  board  and  demonstrate  it.  What  is  the 
angle  of  incidence  ?  What  that  of  reflection  ?  How  does  this  law 
apply  to  curved  surfaces  ?  55.  What  becomes  of  a  ray  of  light  when 
it  falls  perpendicularly  on  a  transparent  surface  ?  When  obliquely  ? 
Demonstrate  it  on  the  black-board  from  the  diagram.  Give  the 
definition  of  the  law  of  refraction.  Which  way  is  the  ray  bent  ? 


AMOUNT  OP  REFRACTION. 


4.5 


the  ray  is  bent  or  refracted  towards  a  line  perpendicular  to 
that  point  of  the  surface  on  which  the  light  falls,  and  from  a 
denser  to  a  rarer  medium  the  law  is  reversed. 

A  common  experiment,  in  illustration  of  this  law,  is  to 
place  a  coin  in  the  bottom  of  a  bowl,  so  situated  that  the 
observer  cannot  see  the  coin  until  water  is  poured  into  the 
vessel ;  the  coin  then  becomes  visible,  because  the  ray  of 
light  passing  out  of  the  water  from  the  coin,  is  bent  towards 
the  eye.  In  the  same  manner,  a  straight  stick  thrust  into 
water  appears  bent  at  an  angle  where  it  enters  the  water. 

56.  Amount  of  Refraction. — The  obliquity  of  the  ray  to 
the  refracting  medium,  determines  the  amount  of  refraction. 
The  more  obliquely  the  ray  falls  on  the  surface,  the  greater 
the  amount  of  refraction.  A  little  modification  of  the  last 
figure  will  make  this  clear.  Let  R  A  be  a  beam  of  light 
falling  on  a  refracting  medium,  it 
is  bent  as  before  to  R'.  If  we 
draw  a  circle  about  A  as  a  centre, 
and  a  line  a  a,  from  the  point  a 
where  the  circle  cuts  the  ray  R  at 
right  angles,  to  the  perpendicular 
passing  through  A,  the  line  a  a  is 
called  the  sine  of  the  angle  of  inci- 
dence ;  while  the  line  a'  a'  is  called 
the  sine  of  the  angle  of  refraction. 

If  a  more  oblique  ray  r,  cuts  the  circle  at  6,  the  line  b  b 
will  be  longer  than  the  line  a  a,  inasmuch  as  the  angle  b  A  a, 
is  greater  than  the  angle  a  A  a. 

The  line  measuring  the  obliquity  before  refraction,  when 
the  ray  passes  into  a  denser  medium,  is  always  greater  than 
that  which  measures  it  after,  and  is  nearly  one-third  more  in 
the  case  of  water.  This  is  called  the  index  of  refraction  ; 
the  refractive  power  of  water  is  expressed  by  1^  or  1-33, 
while  common  glass  with  a  higher  refractive  power,  has  the 
index  of  refraction  1J  or  1'5,  and  the  diamond  2-239.  In 


What  two  common  illustrations  of  this  law  are  named  ?  56.  What 
determines  the  amount  of  refraction  ?  Show  how  this  can  be  demon- 
strated by  an  alteration  of  the  last  figure.  What  is  the  line  a  a 
called  ?  What  is  a  a,  called  ?  What  is  said  of  the  line  measuring 
the  obliquity  before  refraction  and  after  ?  How  much  greater  in  the 
case  of  water?  What  is  it  called  ?  What  is  the  refractive  index 
of  water  ? 


4-6  LIGHT. 

the  larger  works  full  tables  will  be  found  with  the  refractive 
indices  of  numerous  substances. 

57.  Substances  of  an  inflammable  nature,  or  containing 
carbon,  and  those  which  are  dense,  have,  as  a  general  thing, 
a  higher  refracting  power  than  others.  Sir  Isaac  Newton 
observed  that  the  diamond  and  water  had  both  high  refracting 
powers,  and  he  sagaciously  foretold  the  fact,  which  chemis- 
try has  since  proved,  that  both  these  substances  had  a  com- 
bustible base,  or  were  of  an  inflammable  nature.  We  now 
know  that  the  diamond  is  pure  carbon,  and  that  water  has 
hydrogen,  a  combustible  gas,  as  one  of  its  constituents. 

58.  Prism. — In  the  cases  of  sim- 
R'plc  refraction  just  explained  the  ray, 
afler  leaving  the  refracting  medium, 
goes  on  in  a  course  parallel  to  its 
original  direction,  because  the  two  sur- 
faces of  the  medium  are  parallel.  If,  however,  we  employ  a  tri- 
angular jjlass  prism  like  the  figure,  or  any  other  surfaces  not 
parallel,  the  ray  will  be  diverted  permanently  from  its  original 
direction  after  leaving  the  prism.  As  already  explained,  the  ray 
R  is  bent  towards  a  perpendicular  to  the  surface,  (which  is  the 
dotted  line,)  but  on  leaving  the  prism  it  is  by  the  same  law  fur- 
ther refracted  in  the  direction  R';  and  by  altering  the  form  of 
the  surfaces  we  may  thus  send  it  in  almost  any  direction,  as 
in  the  common  multiplying-glass,  which  gives  as  many  im- 
ages as  it  has  faces,  and  all  in  different  directions.  In  this 
way  it  is  that  concave  metallic  mirrors  concentrate  and  convex 
ones  disperse  a  beam  of  liiiht. 

59.  Analysis  of  Light. — By  means  of  the  prism  we  learn 

that  a  beam  of  sun- 
light is  not  simple 
white  light,  but  a 
compound  of  seve- 
ral colors  of  the 
most  vivid  tints 
which  can  be  im- 
agined. We  are  indebted  to  Sir  Isaac  Newton  for  this  beau- 


u 


57.  What  is  said  of  inflammable  substances  ?  What  was  Newton's 
conjecture  about  diamonds  and  water  ?  What  uo  we  now  know  of. 
them  ?  58.  If  the  surfaces  of  the  refracting  medium  are  not  parallel, 
how  is  the  ray  affected  ?  Explain  this  by  the  figure.  Give  an  instance 
of  the  application.  59.  What  do  we  learn  by  means  of  the  prism  ? 
Who  discovered  this,  and  what  is  it  called  ? 


PRISMATIC  COLORS.  47 

tiful  experiment,  which  is  called  Newton's  Analysis  of  Light. 
A  beam  of  sunlight  from  R,  in  the  figure,  falling  from  a 
small  circular  aperture  in  the  shutter  of  a  darkened  room  on 
a  common  triangular  prism,  is  refracted  twice,  and  bent  up- 
ward towards  the  white  screen  R',  placed  at  some  distance 
from  the  prism,  where  it  forms  an  oblong  colored  image, 
composed  of  seven  colors.  This  image  is  called  the  pris- 
matic or  solar  spectrum. 

The  light  from  flames  of  all  kinds,  the  oxy-hydrogen 
blowpipe,  and  the  electric  spark,  or  galvanic  light,  is  also 
compound  in  its  nature,  like  that  of  the  sun  and  other  celes- 
tial bodies. 

60.  Prismatic  Colors. — The  colors  of  the  solar  spectrum 
are  in  the  following  order,  upwards :  red,  orange,  yellow, 
green,  blue,  indigo,  violet.  These  colors  are  of  very  dif- 
ferent refrangibility,  and  for  this  reason  are  presented  in  a 
broad  surface,  the  red  being  the  least  refracted,  and  the  violet 
the  most.  The  seven  colors  of  Newton,  it  is  believed,  are 
really  composed  of  the  three  primitive  ones,  red,  yellow,  and 
blue.  This  idea  is  well  expressed  in  the  following  diagram. 

The  three  primitive         BLTnr.       TKLt,0w.  RED.     SOLAR  SPECTRUM. 

colors  each  attain 
their  greatest  in- 
tensity in  the  spec- 
trum at  the  points 
marked  at  the  sum- 
mit of  the  curves ; 
while  the  four  other 
colors,  violet,  indi- 
go, green,  and  orange,  are  the  result  of  a  mixture,  in  the 
spectrum,  of  the  other  three.  A  portion  of  proper  white  light 
is  also  found  in  all  parts  of  the  spectrum,  which  cannot  be 
separated  by  refraction.  We  may  hence  infer  that  there  is 
a  portion  of  each  color  in  every  part  of  the  spectrum,  but 
that  each  is  most  intense  at  the  points  where  it  appears 


Explain  from  the  figure  how  this  is  done.  Is  the  image  on  the  screen 
circular  ?  What  name  is  given  to  the  image  ?  How  many  colors 
are  in  it  ?  Why  do  we  say  the  light  is  analyzed  ?  Is  light  from 
other  sources  compound  ?  60.  Give  the  order  of  the  colors  in  the 
solar  spectrum.  Why  are  these  colors  separated  to  different  parts 
of  the  spectrum  ?  Which  is  most  bent,  and  which  least  ?  What 
are  the  three  primitive  colors  ?  Explain  the  diagram,  and  how  the 
three  united  form  the  seven.  Is  each  color  pure,  or  mixed  with 
some  white  light  ?  When  most  pure  ? 


48  LIGHT. 

strongest.  The  light  is  most  intense  in  the  yellow  portion, 
and  fades  toward  each  end  of  the  spectrum. 

Sir  John  Herschel  has  detected  rays  of  greater  refrangi- 
bility  than  the  violet  of  the  spectrum,  which  have  a  lavender 
color.  They  have  this  color  after  concentration,  and  are 
therefore  not  merely,  as  might  be  supposed,  dilute  violet  rays. 

If  the  spectrum  is  formed  by  a  beam  of  light  passing 
through  a  slit  not  over  -j^th  of  an  inch  in  width,  the  image 
will  be  crossed  by  a  number  of  dark  lines,  which  always 
appear  in  the  same  relative  position.  These  are  called  the 
Jlxed  lines  of  the  spectrum,  and  are  much  referred  to  as 
boundary  lines  in  optical  descriptions.  These  lines  can  be 
transferred  to  the  sensitive  papers  used  in  photography. 

61.  Natural  Color  of  Bodies. — The  color  of   bodies 
nature  are  due  to  the  fact  that  their  surfaces  absorb  all  the 
light,  except  the  color  we    recognise  as   belonging  to  each 
object.     This  property  is  to  be  ascribed  to  some  cause  in- 
herent in  the  nature  of  the  substances. 

62.  Double  Refraction. — The  refraction  which  we  have 
just  considered,  belongs  to  all  bodies  which  permit  the  pass- 
age of  light.     Rut  in   most  crystalline  substances,  and  all 
bodies  having  any  regular  internal  structure,  such  as  bone, 
shell,  &c.,  there  is  another   sort  of  refraction.     By  looking 
through  such  bodies  in  certain  positions,  two  objects  are  seen 
instead  of  one,  one  by  the  ordinary,  and  the  other  by  an  ex- 
traordinary ray. 

This  phenomenon  is  called  Double  refraction,  and  is  best 
seen  in  the  mineral  called  calc  spar,  or  Iceland  spar,  which, 
when  pure,  is  colorless  and  transparent,  and  breaks  into  regular 
rhombs,  with  brilliant  faces.  If  a  rhomb  of  this  mineral  be 
laid  over  a  black  line,  we  see  a  double  image,  as  if  there  were 
in  reality  two  lines.*  This  direction  of  the  ray  is  owing  to 

What  is  lavender  light  ?  Describe  the  lines  observed  in  the  spec- 
trum. 61.  Give  the  cause  of  the  color  of  natural  bodies.  62.  How 
generally  is  simple  refraction  found  in  transparent  bodies  ?  What 
bodies  have  another  sort  of  refraction  ?  What  is  seen  on  looking  through 
such  bodies  ?  What  is  this  property  called  ?  In  what  best  seen  ? 

*  A  sharp  line  like  p  g,  when  seen 
through  a  rhomb  of  calc  spar  in  the  direc- 
tion of  the  ray  R  r,  will  seem  to  be  dou- 
ble, a  second  parallel  line  m  n,  being 
seen  at  a  short  distance  from  it,  and 
the  dot  o,  will  have  its  fellow  e.  In  this 
case  the  light  is  represented  as  coining 
from  R  to  r,  and  passing  through  the  crys- 


POLARIZATION.  49 

the  interior  crystalline  structure  of  the  mineral.  Of  the  two 
beams  into  which  the  light  is  divided,  one  obeys  the  law  of 
refraction  already  explained,  while  the  other  pursues  an  en- 
tirely different  course.  One  is  called  the  ordinary,  and  the 
other  the  extraordinary  ray. 

63.  Polarization. — The  light  which  has  passed  one  crys- 
tal of  Iceland  spar  by  extraordinary  refraction,  is  no  longer 
affected  like  common  light.  If  we  attempt  to  pass  it  through 
another  crystal  of  the  same  substance,  there  will  be  no  fur- 
ther subdivision,  and  only  a  greater  separation  of  the  two 
beams. 

This  peculiar  physical  change  is  called  polarization,  as 
the  light  is  supposed  to  assume  a  polar  condition.  Many 
other  mineral  substances  also  polarize  light  when  cut  into 
thin  plates.  The  mineral  called  tourmaline  has  this  property 
in  a  remarkable  degree.  The  internal  structure  of  this 
mineral  is  such,  that  a  ray  of  light  can  pass  through  thin 
plates  of  it  in  one  direction,  but  not  in  another ;  as,  for  illus- 
tration, a  thin  blade  may  pass  between  the  wires  of  a  cage  if 
held  parallel  to  the  interstices,  but  will  of  course  be  arrested 
if  turned  at  right  angles  to  them. 

In  the  annexed 
figure  we  have  two 
thin  plates  of  tour- 
maline placed  par- 
allel to  each  other 
in  the  same  direc- 
tion. A  ray  of 
light  passes  through 
both  in  the  direction  of  R  R',  and  apparently  suffers  no 


What  is  this  property  owing  to  ?  Explain  the  figure  in  the  note, 
on  the  board.  63.  How  is  the  ray  which  has  passed  one  crystal  of 
calc  spar  affected  by  another  ?  What  is  this  change  called  ?  In  what 
else  is  it  seen  ?  How  is  it  illustrated  ?  Explain  the  figures  of  the 
tourmaline  plates. 


tal,  it  is  split  and  emerges  in  two  beams  at  e  and  o.  The  same 
effect  would  be  produced  if  the  light  fell  so  as  to  strike  any  part  of  the 
imaginary  plane  A  C  B  D,  which  diagonally  divides  the  crystal,  and  is 
called  its  principal  section.  The  axis  or  line  drawn  from  A  to  B,  is 
contained  in  this  plane.  But  if  we  look  through  the  crystal  in  a  di- 
rection parallel  to  this  plane  (A  C  B  D)  there  is  only  simple  refrac- 
tion, and  only  one  line  is  seen. 
5 


50  LIGHT. 

change :  if  however,  these  plates  are  so  placed  as  to  cross 
each  other  at  right  angles,  as  in  the  second  figure,  the  ray  of 
light  is  totally  extinguished ;  and  four  such  points  may  be 
found  in  revolving  one  of  the  plates  about  the  ray  as  an  axis. 

64.  Light  is  also  polarized  when  passed  obliquely  through 

a  bundle  of  plates  of  thin  glass,  or  mica, 
arranged  as  in  the  figure.  The  reflection  of 
light  from  the  surface  of  various  substances  is 
also  productiveof  polarization,  at  an  angle  which 
is  peculiar  to  each  substance,  and  hence  called 
the  angle  of  polarization.  This  angle  on  glass 
is  found  to  be  56°48'.  The  phenomena  of 
polarized  light  are  among  the  most  attractive 
and  important  in  the  science  of  optics,  but 
their  study  would  lead  us  away  from  our  pre- 
sent object. 

65.  Chemical  Rays. — Besides  the  rays  of  light  in  the  so- 
lar spectrum  which  we  have  already  noticed,  and  the  rays  of 
heat  which  we  shall  presently  consider,  there  is  still  another 
class  of  rays,  which,  while  they  have  a  greater  refrangibility 
than  the  violet,  are  also  found  by  the  delicate  experiments  of 
Herschel,  to  be  present  in  every  part  of  the  solar  spectrum : 
they  have  been  sometimes  called  the  chemical  rayx,  from  the 
powerful  effect  which  they  produce  in  chemical  combinations. 
They  act  in  a  manner  altogether  independent  of  the  rays  of 
heat.     Chlorine  and  hydrogen  gases  are  made  to  combine  by 
them  with  explosive  energy,  while  in  diffuse  light  the  union 
of  these  gases  is  slow  and  quiet. 

Many  metallic  salts  are  changed  to  a  darker  color  by  their 
action,  as  the  chlorid  and  iodid  of  silver,  facts  which  have 
been  beautifully  applied  in  the  arts  of  photography  by  sensi- 
tive papers,  and  of  the  daguerreotype.  The  last  depends  on 
the  sensitiveness  of  the  iodid  of  silver  to  the  action  of  the 
chemical  or  more  luminous  rays  of  the  sun.  This  power  in 
the  non-luminous  rays  has  been  variously  designated  by  the 
terms  actinism,  tithonicity,  and  energia. 

66.  The  accompanying  diagram  will  enable  the  student  to 


64.  How  else  is  light  polarized  ?  How  by  reflection  ?  What  is 
the  angle  called  ?  What  is  it  for  glass  ?  65.  What  other  class  of 
rays  is  named  ?  How  do  they  act  ?  Give  examples  of  their  effects. 
What  arts  are  dependent  on  the  chemical  rays  ?  What  has  this 
power  been  called  ? 


CHEMICAL  RAYS.  51 

obtain  clearer  views  of  our  present  knowledge  in  relation  to 
this  interesting  subject,  which  has  already  made  so  many 
splendid  presents  to  the  arts.  From  A  to  B,  we  have  the 
solar  spectrum  with  the  colors  in  the  same  order  as  already 
described,  (60.)  The  greatest  chemical  power  is  at  the  vio- 
let, and  the  greatest  heat  at  the  red  ray.  At  b  another  red  ray 
is  discovered,  and  at  a  is  the  lavender  light.  The  luminous 
effects  are  shown  by  the  curved  line  C,  the  maximum  of  light 
being  found  at  the  yellow  ray.  The  point  of  greatest  heat  is 
at  D,  beyond  the  red  ray,  and  d 

it  gradually  declines  to  the 
violet  end,  where  it  is  entirely 
wanting,  the  other  limit  of  heat 
being  at  c.  The  chemical 
powers  are  greatest  about  E, 
in  the  limits  of  the  violet,  and  2 

gradually  extend  to  d,  where  VIOLW, 
they  are  lost.  They  disap-  INDI00' 
pear  also  entirely  at  C,  the  BLUB, 
yellow  ray,  which  is  neutral  in  ORKEN> 
this  respect,  attain  another  TKLLOW 
point  of  considerable  power  at  °*pN01 
F,  in  the  red  ray,  which  gives  ^i 

its  own   Color   to   photographic  EXTREME  RED, 

pictures ;  and  ceases  entirely 
at  e.  The  points  Z>,  C,  £, 
therefore,  represent  respective- 
ly the  three  distinct  phenomena 
of  Heat,  Light,  and  Chemical 
Power.  This  last  is  believed  to  be  quite  independent  of  the 
other  powers ;  for  all  light  may  be  removed  from  the  spec- 
trum by  passing  it  through  blue  solutions,  and  yet  the  chemi- 
cal power  remains  unaltered.  \/ 

67.  Spectral  Impressions. — ificbnnection  with  the  chemi- 
cal properties  of  light,  we  mention  the  curious  fact  that  bodies 
have  the  power  of  impressing  their  images  or  pictures  on  each 
other  in  the  dark,  or  on  plates  of  polished  metal  and  glass, 
in  such  a  manner  that  these  become  at  once  visible,  if  the 
bright  surface  be  breathed  on  or  exposed  to  the  vapor  of 

Explain  the  diagram  illustrating  the  points  of  greatest  light,  heat, 
and  chemical  action.  What  is  found  at  Fon  the  scale  ?  Is  the  chem- 
ical power  independent  of  light  ?  67.  What  are  spectral  impressions  ? 


52  LIGHT. 

mercury,  as  in  the  daguerreotype.  If  a  coin  or  medal  is 
placed  on  a  finely  polished  surface  of  sheet-copper  or  silver, 
and  be  left  in  a  perfectly  dark  place  for  a  few  hours,  (parti 
cularly  if  the  plate  has  been  warmed,)  it  will  be  found  that 
on  breathing  upon  or  mercurializing  the  metallic  surface,  an 
image  of  the  object  will  at  once  be  brought  out,  and  can  be 
renewed  in  the  same  manner  indefinitely.  It  is  supposed 
that  this  eflect  is  owing  to  an  invisible  influence,  passing  be- 
tween the  two  objects,  and  producing  a  change  in  the  condition 
of  the  surface,  or  the  arrangement  of  its  particles.  Engrav- 
ings can  be  permanently  copied  in  this  way,  and  many  curi- 
ous and  instructive  experiments  performed,  which  our  space 
will  not  permit  us  to  describe. 

68.  Phosphorescence  is  a  property  possessed  by  some 
bodies  of  emitting  a  feeble  light,  often  at  ordinary  tempera- 
tures. The  diamond  and  some  other  substances,  after  being  ex- 
posed to  the  rays  of  the  sun,  will  emit  light  for  some  time  in  the 
dark.  Fluor-spar,  feld-spar,  and  some  other  minerals,  give  out 
a  fine  light  of  varied  hues,  when  gently  heated  or  scratched. 
Oyster-shells  which  have  been  calcined  with  lime  and  exposed 
to  the  sun-light,  will  shine  in  a  dark  place  for  a  considerable 
time  afterwards.  The  glow-worm,  the  fire-fly,  rotten  wood, 
decaying  fish,  and  various  marine  animals,  possess  the  same 
property  in  a  greater  or  less  degree. 

This  and  similar  facts,  have  been  made  the  basis  of  an 
argument  by  Dr.  Draper,  to  sustain  the  opinion  that  there  is, 
in  addition  to  light,  heat,  and  electricity,  a  fourth  imponderable 
agent. 

This  brief  outline  of  the  history  of  light,  must  impress  the 
belief  that  this  agent  holds  a  most  important  place  in  main- 
taining the  physical  welfare  of  our  planet. 

Plants,  by  aid  especially  of  the  yellow  rays,  transform  the 
inorganic  constituents  of  matter  into  living  and  growing  or- 
ganisms, which  appropriate  their  food,  decompose  and  recom- 
pose  various  compounds  in  a  manner  which  the  chemist  can 
never  hope  to  imitate. 

How  are  they  produced  ?  68.  What  is  phosphorescence  ?  What 
substances  possess  it  ?  What  opinion  has  been  based  on  such  facts  ? 
What  is  said  of  the  importance  of  light  ?  How  are  fluids  affected  by 
it  ?  Which  ray  is  effectual  in  vegetation  ? 


SOURCES  OP  HEAT.  53 


III.  HEAT. 

69.  All  our  knowledge  of  heat  is  confined  to  its  effects. 
We  experience  a  sensation'  on  coming  near  to,  or  touching 
other  bodies,  which  we  call  heat  or  cold,  according  as  they 
have  a  higher  or  lower  temperature  than  ourselves.     This  is 
the  common  use  of  the  word.     In  chemical    language,  we 
mean  by  heat,  the  unknown  cause  of  the  effects  produced  by 
it  on  bodies,  and  not  the  sensation.     We  are  as  ignorant  of 
the  real  nature  of  heat  as  we  are  of  that  of  light.     It  is  often 
called  an  imponderable  agent,  as  has  been  before  mentioned, 
because  we  can  find  no  increase  of  weight  in  bodies  by  heat- 
ing them,  nor  any  decrease  in  weight  by  cooling  them.     The 
changes  which  heat  has  power  to  work  on  matter  are  wonder- 
ful; and  as  it  is  one  of  the  most  important  of  chemical  agents, 
we  shall  be  well  employed  in  the  study  of  its  phenomena. 

Without  pausing,  therefore,  to  consider  any  of  the  inge- 
nious theories  which  have  been  proposed  regarding  the  nature 
of  heat  and  its  relations  to  matter,  we  will  proceed  to  con- 
sider its  sources  and  effects. 

70.  Sources  of  Heat. — 1st.  The  sun  is  the  great  source 
of  heat.     His  rays  alone  make  the  earth  inhabitable ;  with- 
out  them,  this  world  would  be  only  a  barren  waste,  and  its 
waters  would  be  as  solid  and  unalterable  as  granite.     All  the 
combustible  material  on  or  in  the  earth,  would  not  supply  the 
want  of  the  sun  for  a  single  day. 

2d.  Combustion  is  another  source  of  heat.  Our  fires  give 
us  warmth,  because  the  combustible  part  of  the  fuel  takes  on 
a  new  form  of  existence,  combining  chemically  with  one 
portion  of  the  atmosphere,  and  evolving  heat.  This 
source  of  heat,  then,  is  due  to  a  change  of  state  in  bodies. 
The  same  cause  we  shall  also  see,  further  on,  (111,)  may 
sometimes  be  a  source  of  cold,  that  is,  of  a  diminution  of 
heat.  This  source  of  heat  is  entirely  limited  by  the  amount 
of  the  substances  suffering  change,  and  ceases  when  the  change 
is  complete. 


69.  What  do  we  know  of  the  nature  of  heat?  Distinguish  be- 
tween its  nature  and  our  sensations.  70.  Name  the  first  source  of  heat. 
The  2d.  Why  does  the  fire  warm  us  ?  What  limits  this  source  of 
heat? 

5* 


54  HEAT. 

3d.  Friction  is  a  third  source  of  heat.  Heat  is  generated 
by  friction  to  an  indefinite  amount,  as  in  the  rubbing  together 
of  two  limbs  in  a  forest,  moved  by  violent  winds,  by  which 
it  is  said  that  so  much  heat  has  been  excited  as  to  set  fire  to 
large  tracts  of  timber-land.  Savage  nations,  by  rubbing  two 
sticks  violently  together,  are  accustomed  to  produce  fire. 
Large  plates  of  iron  have  been  made  to  move  slowly  over 
each  other,  by  water-power,  thus  producing  heat  enough  to 
warm  extensive  buildings.  The  water  beneath  which  cannon 
are  bored  becomes  very  hot,  from  the  friction  of  the  borer 
against  the  metal  which  it  cuts.  The  principal  thing  to  be 
remarked  in  reference  to  this  source  of  heat  is,  that  it  seems 
to  be  without  limit,  so  long  as  motion  is  continued  ;  and  that 
the  substances  used  to  produce  friction  do  not  necessarily 
suffer  any  permanent  change  of  state.  The  evolution  of  heat 
goes  on,  the  substances  acted  on  neither  increasing  nor  dimin- 
ishing in  quantity,  while  the  body  retains  its  chemical  pro- 
perties unaltered. 

4th.  A  fourth  source  is  Electricity,  and  it  is  probably 
very  closely  allied  to  the  second.  The  spark  from  the  elec- 
trical machine,  the  galvanic  current,  and  the  lightning,  are 
alike  sources  of  heat. 

We  might  also  mention  the  warmth  of  our  own  bodies, 
and  the  whole  animal  world,  as  another  source  of  heat ;  but 
it  seems  more  than  probable  that  animal  heat  is  only  the 
result  of  chemical  changes  going  on  in  the  process  of  respi- 
ration, and  the  other  functions  of  the  body,  and  as  such  be- 
Igngs  to  the  second  source,  already  mentioned. 

5lh.  Geology  teaches  us  that  the  interior  of  the  earth  is 
in  a  state  of  intense  ignition,  amounting  at  times  to  fluidity, 
as  is  proveu1  by  the  eruptions  of  lava  from  active  volcanoes. 
All  the  excavations  for  mines  and  artesian*  wells  which  have 
been  made  have  shown,  that  as  we  descend,  the  temperature 
f  of  the  earth  constantly  increases,  after  we  have  passed  below 

What  is  said  of  friction  ?  Give  examples  of  heat  thus  produced. 
What  is  said  of  electricity  and  animal  heat  ?  What  has  geology 
taught?  State  the  facts.  Does  heat  from  these  various  sources 
differ  in  kind  ? 


*  Artesian  wells  are  borings  made  with  an  auger,  usually  to  a 
great  depth,  and  are  so  called  from  the  province  of  Artois  in  France, 
where  they  were  first  made. 


EXPANSION.  55 

the  influence  of  the  atmosphere.  This  increase  amounts  to 
about  1°  of  Fahrenheit's  thermometer  for  every  40  or  45  feet 
of  descent.  The  celebrated  well  of  Grenelle,  at  Paris,  (which 
is  an  artesian  boring,)  is  1794  feet  deep,  and  its  temperature 
is  82°,  which  is  31°  above  the  mean  temperature  of  Paris; 
and  the  well  at  Mondorf,  in  the  Duchy  of  Luxemburg,  is 
2200  feet  deep,  and  the  water  rises  with  a  temperature  of  95° 
Fahrenheit.  This  increase  of  temperature,  if  continued  at 
the  same  rate,  would  give  us  boiling  water  at  about  two  miles 
from  the  surface.  At  ten  miles,  all  solid  substances  would 
become  intensely  red ;  and  at  thirty  or  forty,  all  known  solids 
would  be  in  a  state  of  fusion.  No  doubt  the  central  heat 
of  the  earth,  escaping  by  insensible  degrees  to  the  surface, 
has  had  an  important  influence  on  its  condition. 

From  whatever  source  heat  may  be  derived,  its  effects  on 
matter  are  the  same,  and  we  will  first  consider  one  of  its  most 
general  powers,  namely, — 


1.  Expansion. — The  effect  of  Heat  in  altering  the  dimen- 
sions of  Bodies. 

71.  Heat  has   been  called    the  antagonist  of  attraction: 
while  the  latter  power  acts  to  bind  together  the  particles  of 
matter,  heat  tends  to  separate  them.     We  see  about  us  mat- 
ter in  the  different  forms  of  solids,  liquids,  and  gases  or  vapors. 
Water  presents  a  familiar  instance  of  a  substance  known  to 
us  in  all  three  of  these  states ;  as  a  solid  in  ice,  a  liquid  at 
common  temperatures,  and  an  invisible  vapor  at  higher   tem- 
peratures.    The  sole  cause,  so  far  as  we  know,  of  this  change 
of  state  in  water,  is  variation  of  temperature. 

72.  We  have  before  seen  (26)  the  remarkable  power  of 
elasticity  in  expanding  air  and  other  gases.     Heat  produces 
expansion  in  all  bodies,  even  the  most  firm ;  and  this  is  so 
powerful  as  to  set  at  defiance  all  attempts  to  restrain  it. 

73.  To  show  the  expansion  of  a  solid,  a  bar  of  metal 


What  is  said  of  the  well  at  Grenelle  ?  What  would  happen  if  the 
ratio  of  increase  of  temperature  continued  the  same  ?  71.  Of  what 
is  heat  the  antagonist  force  ?  Illustrate  this.  72.  What  power  of 
heat  do  we  now  consider  ? 


56  HEAT. 

is  provided  with  a  handle,  (see  an- 
nexed figure,)  which  at  ordinary  tem- 
peratures, exactly  fits  a  gauge;  on 
heating  this  over  a  spirit-lamp,  or 
by  plunging  it  into  hot  water,  it  will 
be  so  much  swelled  (expanded)  in 
all  its  dimensions,  as  no  longer  to 
enter  the  gauge.  On  cooling  it  with 
ice,  it  will  again  not  only  enter  freely, 
but  with  room  to  spare.  The  same 
fact  is  shown  by  a  small  cannon-ball, 
to  which,  when  cold,  a  ring  with  a 
handle  will  exactly  fit,  but  on  heating  the  ball  in  the  fire,  the 
ring  will  no  longer  encircle  it. 

74.  The  expansion  of  a  fuid  may  be  shown  by  filling 
the  bulb  of  a  large  tube  a  with  colored 
fluid  to  a  mark  on  the  stem.  On  plung- 
ing the  bulb  into  hot  water,  the  fluid  is 
seen  to  rise  rapidly  in  the  stem.  If  it 
be  cooled  by  a  mixture  of  ice  and  water, 
it  is  seen  to  sink  considerably  below  the 
II  "  line.  A  similar  bulb  6,  filled  with  air, 

and  having  its  lower  end  under  water, 
is  arranged  as  in  the  figure  to  show  the 
€|j3  JJ|  expansion  of  air  by  heat.     The  warmth 
^;x  ^-Ipjg   of  the  hand  applied  to  the  naked  ball 

^  JaS  t^^Sfi    w*^  k°  sufficient  to  cause  bubbles  of  air 

^•^^    to  escape  from  the  open  end  through  the 
water,  and  on  removing  the  hand,  the 
contraction  of  the  air  in  the  ball,  from  the  cooling  of  the 
surface,  will  cause  a  rise  of  the  fluid  in  the  stem,  correspond- 
ing to  the  volume  of  air  expelled,  as  shown  in  the  figure. 
The  slightest  change  of  temperature  will  cause  this  column 
«  of  fluid  to  move,  as  the  air  expands  or  contracts.     We  thus 
prove  experimentally  that  solids,  fluids,  and  gases,  expand  by 
an  increase,  and  contract  by  a  decrease  of  temperature. 

75.  Thermometers. — The  law  of  expansion  enables  us  to 
construct  an  instrument  by  which  we  can  measure  changes 
of  temperature  with  accuracy.  Such  an  instrument  is  the 


73.  Illustrate  the  expansion  of  a  solid.  74.  Illustrate  expansion  in  a 
fluid ;  (a)  in  water,  (5)  in  a  gas.  75.  What  instrument  does  the  law 
of  expansion  give  us  ? 


EXPANSION.  57 

Thermometer.*  Hot  and  cold  are  terms  of  comparison  only, 
and  teach  us  nothing  of  the  real  difference  of  temperature 
which  bodies  may  possess.  If  we  place  one  hand  in  a  vessel 
of  iced  water,  and  the  other  in  moderately  warm  water,  we 
at  once  perceive  a  strong  contrast ;  but  if  we  suddenly  plunge 
both  hands  into  a  third  vessel  of  water  at  the  common  tempe- 
rature, our  sensations  are  at  once  reversed ;  the  third  vessel 
is  warm  as  compared  with  ice- water,  and  cold  as  compared 
with  the  tepid  water.  The  thermometer,  however,  enables 
us  with  the  greatest  ease  to  obtain  accurate  notions  of  these 
comparative  temperatures. 

This  valuable  instrument  was  first  constructed  by  Sanc- 
torio,  an  Italian  philosopher,  about  A.  D.  1590.  Sanctorio's 
instrument  was  what  is  now  called  an  air-thermom-  ^^ 
eter,  because  a  confined  portion  of  air  is  employed 
to  show  the  changes  of  temperature.  The  annexed 
figure  shows  the  arrangement  of  the  parts.  A  bulb 
of  glass  with  a  long  stem  is  placed  with  its  mouth 
downwards,  in  a  vessel  containing  a  portion  of 
colored  water.  A  part  of  the  air  is  expelled  from 
the  ball  by  expansion,  (74,)  which  causes  the  fluid 
to  rise  to  a  convenient  point  in  the  stem,  to  which 
is  attached  a  scale  of  equal  parts,  with  degrees  or 
divisions  marked  by  some  arbitrary  rule.  Thus 
arranged,  the  instrument  indicates  with  great  deli- 
cacy any  change  of  temperature  in  the  surrounding 
air.  The  portion  of  air  confined  in  the  ball,  when 
heated  in  any  degree,  expands,  and  pressing  on  the  column 
of  fluid  in  the  stem  drives  it  down,  according  to  the  amount 
of  expansion  or  the  degree  of  heat ;  and  the  reverse  results 
from  a  decrease  of  temperature ;  the  confined  air  then  con- 
tracting occupies  less  room,  and  the  fluid  rises.  The  air- 
thermometer  is  very  delicate,  but  is  too  limited  in  its  range  to 
supply  the  wants  of  science ;  it  has  given  place  to  the — 

76.  Mercurial^  or  Common  Thermometer,  which  is  now 
in  every  house.  This  instrument  indicates  changes  of  tem- 

What  does  this  instrument  enable  us  to  do  ?  Illustrate  the  inaccu- 
racy of  our  sensations.  Who  invented  the  thermometer,  and  when  ? 
Explain  his  instrument.  76.  What  instrument  is  now  used  in  place 
of  the  air-thermometer  ? 


*  Named  from  the  Greek  thermos,  warmth,  and  metron,  measure. 


58  HEAT. 

perature  by  the  expansion  of  a  fluid  in  a  vacuum.  It  is  form- 
ed of  a  small  glass  tube  with  a  very  fine  bore,  (a  capillary 
tube,  21,)  on  one  end  of  which  is  blown  a  small  boll  or  bulb 
to  contain  the  mercury,  or  other  fluid  with  which  it  is  filled. 
This  instrument  is  made  by  a  process  which  gives  us  a  fine 
illustration  of  several  principles  already  explained,  which  we 
will  briefly  describe. 

It  would  be  impossible  to  pour  any  fluid  (much  less,  mer- 
cury) into  so  small  an  opening  as  the  fine  hair-line  of  a 
thermometer-bore.  If,  however,  we  cautiously  hold  the  ball 
of  the  lube  in  the  flame  of  a  small  alcohol-lamp,  the  heat, 
expanding  the  air  which  it  contains,  will  drive  out  a  portion 
of  it  at  the  open  end,  which  is  held  under  the  surface  of  a 
small  quantity  of  mercury,  and  the  air  will  be  seen  escaping 
in  bubbles  through  it.  Let  us  hold  the  tube  as  nearly  hori- 
zontal as  possible,  and,  still  keeping  its  open  end  under 
the  mercury,  withdraw  the  ball  from  the  heat ;  as  it  gradually 
cools,  the  contraction  of  the  remaining  portion  of  the  air 
within  the  ball,  (27,)  aided  by  the  pressure  of  the  air  on  the 
surface  of  the  mercury,  (33,)  will  cause  the  fluid  to  rise 
rapidly  in  the  tube,  and  we  shall  presently  see  it  fall,  drop  by 
drop,  into  the  empty  ball,  until  (if  the  process  has  been  well 
performed)  it  is  nearly  filled.  How  shall  we  get  rid  of  the 
remaining  air  in  the  ball  and  tube?  Let  us  fit  a  small  funnel 
or  cone  of  paper  to  the  open  end  of  the  tube,  tie  it  securely 
there,  and  put  into  it  a  little  mercury,  which  will  quite  cover 
the  open  end.  Now  place  the  ball  in  the  lamp-flame  again,  and 
taking  care  not  to  heat  the  stem,  cautiously  warm  the  mer- 
cury, until  the  heavy  fluid  boils  vigorously  in  the  delicate  glass 
ball.  The  air  in  the  tube  is  driven  out  by  the  vapor  of  the 
boiling  mercury,  and  is  seen  to  escape  in  bubbles  through  the 
fluid  metal  in  the  paper  funnel,  which  acts  as  a  valve  (28)  to 
prevent  its  return.  The  whole  space  is  now  full  of  the 
invisible  vapor  of  this  dense  metal,  and  once  more  withdraw- 
ing the  ball  from  the  heat,  the  vapor  is  condensed,  and  the 
pressure  of  the  air  on  the  surface  of  the  mercury  in  the 
funnel,  instantly  forces  it  into  the  vacuum  beneath,  completely 
filling  both  ball  and  stem.  The  operation  of  thermometer- 
making  is  now  completed  by  once  more  warming  the  ball,  to 
expel  any  remaining  portion  of  the  air,  and  also,  if  necessary, 


Give  the  process  of  making  a  thermometer. 


EXPANSION.  59 

a  part  of  the  mercury  in  the  stem,  and  at  the  same  instant 
the  open  end  of  the  tube  is  sealed  by  a  blow-pipe.  On  again 
cooling,  the  mercury  contracts,  and  leaves  a  vacuum  of  the 
most-  perfect  description,  (33.)  We  will  explain  presently 
how  the  thermometer  may  be  fitted  with  a  scale. 

Alcohol  is  also  employed  to  fill  thermometers  which  are  to 
be  used  for  estimating  very  low  temperatures ;  but  mercury 
is  the  fluid  preferred  for  all  common  cases,  because  of  the 
great  uniformity  in  its  rate  of  expansion. 

In  the  arctic  regions,  the  temperature,  for  many  weeks 
together,  is  below  the  freezing  point  of  mercury,  and  there  alco- 
hol thermometers  are  indispensable.  Pure  alcohol  has  never 
been  frozen. 

77.  Graduation  of  tyermometers. — To  make   the  ther- 
mometer of  any  va(ae  as*  an  indicator  of  temperature,  we 
must  have  a  standard  of  comparison,  by  which  two  observers 
with  different  instruments,  and  in  different  parts  of  the  globe, 
may  compare  the   results   of  their   observations.     We   are 
indebted  to  Sir  Isaac  Newton  for  suggesting  the  method  of 
graduating  thermometers.     He   knew  that  ice   melted,  and 
water  boiled,  always  at  the  same  temperatures  at  the  level  of 
the  sea.     By  marking  the  place  where  the  mercury  of  a 
thermometer  stood,  in  boiling  water,  and  also  in  a  mixture  of 
snow  or  ice  with  water,  two  fixed  and  immutable  points  are 
obtained,  the  boiling  and  freezing  of  water,*  which  were  found 
by  repeated  trials,  to  be  at  the  same  relative  distance  in  all 
good   instruments.     By   dividing   the   space   between   these 
points  into  any  number  of  equal  parts,  the  instrument  became 
complete,  and  its  indications  could  be  compared  with  those  of 
any  other,  graduated  on  the  same  plan. 

78.  Thermometrical  Scales. — In  this  country  and  in  Eng- 
land, Fahrenheit's  scale  is  chiefly  employed.     It  is  unfortu- 
nate that  there  should  be  more  than  one  thermometrical  scale  in 


What  is  used  to  fill  thermometers  to  register  extreme  cold  ?  77. 
How  is  one  thermometer  compared  with  another  ?  What  is  New- 
ton's mode  of  graduation  ?  How  is  the  space  between  boiling  and 
freezing  divided  ? 

*  We  shall  see  hereafter  that,  although  the  melting  and  freezing 
of  water  take  place  at  the  same  temperature,  under  favorable  cir- 
cumstances, yet  that  it  is  the  melting  of  ice,  and  not  the  freezing  of 
water,  which  gives  invariably  the  constant  temperature  of  32° — the 
freezing  point  being  liable  to  some  variation. 


60 


HEAT. 


100 


50 


;•• 


.10 


use,  because  it  is  inconvenient  to  translate  the 
terms  of  any  other  nation  into  our  own.  The 
scale  or  division  of  Celsius  (a  Swedish  phi- 
losopher) is  generally  used  at  present  in 
continental  Europe,  and  is  also  called  the 
Centigrade  scale,  because  it  divides  the  in- 
terval between  the  boiling  and  freezing  of 
water  into  one  hundred  parts.  Formerly  the 
French  used  the  graduation  of  Reaumur, 
which  made  80°  between  boiling  and  freezing 
water.  Fahrenheit  (who  was  a  citizen  of 
Amsterdam)  thought  that  he  had  found  the 
true  zero,  or  point  of  greatest  possible  cold, 
by  means  of  a  mixture  of  snow  and  salt. 
We  now  know  that  there  is  no  such  thing  as 
an  absolute  zero*  either  of  heat  or  cold. 
Fahrenheit  divided  his  scale  from  his  supposed 
zero  to  the  boiling  point  of  water  into  212°, 
which  places  the  freezing  of  water  at  32°,  and 
leaves  180°  totwccn  that  point  and  the  boil- 
ing of  water.  Both  Celsius  (Centigrade) 
and  Reaumur  made  the  freezing  of  water  the 
zero  of  their  scales.  The  degrees  of  Centi- 
grade are  always  marked  in  books  C. ;  of 
Reaumur  R. ;  and  of  Fahrenheit  F.,  or  Fahr. 
Therefore  00C.=00R.=32°F.;  and  100°C= 
80°R.=  180°F.  ;  and  keeping  these  propor- 
tions in  mind,  it  is  quite  easy  to  translate  the 
reading  of  one  scale  into  the  other. 

The  figure  annexed  shows  us  at  a 
glance  the  several  scales  compared.  The 
one  on  the  right,  marked  De  Lisle,  was 
the  contrivance  of  a  French  astronomer 


78.  Name  the  principal  thermometrical  scales  ?     What  number  of  * 
degrees   did   Celsius   make   between   boiling  and  freezing  water? 
How  many  are  there  in  Reaumur's  scale  ?     What  was  Fahrenheit's 
zero?     How  many  degrees  had  he  above  zero  to  the  boiling  of 
water  ? 


•  The  word  zero  is  from  the  Italian,  and  signifies  < nothing,'  and 
was  applied  to  the  thermometer  in  allusion  to  the  supposed  absence 
of  all  heat. 


EXPANSION.  61 

who  proposed  to  call  boiling  water  zero,  and  read  down- 
wards, by  150°,  to  the  freezing  point.  It  is  not  used.  We 
shall  use  only  Fahrenheit's  scale,  which  is  so  well  understood 
in  this  country ;  and  a  single  example  will  show  how  we  may 
convert  the  degrees  of  Centigrade  or  Reaumur  into  those  of 
Fahrenheit.  100°C.==800R.=180°F.  is  the  same  as  5C.= 
4R.=9F.  Fahrenheit's  scale  (180°)  is  to  that  of  Reaumur 
(100°)  as  9  is  to  5.  To  reduce  Centigrade  to  Fahrenheit,  we 
can  multiply  by  9  and  divide  by  5,  and  add  32°  to  the  quo- 
tient, and  vice  versa.  Suppose  we  wish  to  know  what  70°C. 
is  on  Fahrenheit's  scale ;  we  have  the  proportion  5:9:: 
70°  :  126°.  If  we  add  32°,  which  is  the  difference  between 
zero  of  F.  and  C.,  we  have  126°  + 32°=  158°,  which  is  the 
number  required,  for70°C.=158°F.  In  stating thermometrical 
degrees,  the  sign  +  is  used  for  points  above  zero,  and  —  for 
those  below. 

79.  The  Self-Registering  Thermometer  (often  called,  also, 
Six's  Thermometer)  is  a  form  of  the  instrument  contrived  for 


the  purpose  of  ascertaining  the  extremes  of  variations  which 
may  occur,  as,  for  instance,  during  the  night,  or  in  sounding 
to  great  depths  in  the  sea,  or  measuring  the  temperature  of 
an  artesian  boring.  It  consists  of  two  horizontal  thermome- 
ters attached  to  one  frame,  as  in  the  figure ;  b  is  a  mercurial 
thermometer,  and  measures  the  maximum  temperature,  by 
pushing  forward,  with  the  expansion  of  the  column,  a  short 
piece  of  steel  wire,  of  such  size  as  to  move  easily  in  the  bore 
of  the  tube ;  it  is  left  by  the  mercury  at  the  remotest  point 
reached  by  the  expansion ;  a  is  a  spirit-of-wine  thermometer,  I 
and  measures  the  minimum  temperature.  It  contains  a  short 
cylinder  of  porcelain,  shown  in  the  figure,  which  retires  with 
the  alcohol  on  the  contraction  of  the  column  of  fluid,  but  does 
not  advance  on  its  expansion.  To  use  the  instrument,  it  is 

How  are  the  degrees  of  one  scale  converted  into  another  ?  Give 
examples.  79.  Explain  Six's  thermometer.  What  registers  the 
maximum  temperature  ? 


62  HEAT. 

necessary  before  every  observation  to  incline  it,  and  with  a 
slight  jar  bring  the  cylinder  of  porcelain  in  a  to  the  surface 
of  the  fluid. 

80.  The  Differential   Thermometer  is  a  form  of  air-ther- 
mometer, (75^)  with  two  bulbs  on  one  tube,  bent  twice  at  right 
angles,  and  supported  as  shown  in  the  figure  ;  a  little  sulphu- 
ric  acid,  water,  or   other   fluid,  partly  fills   the   stem  only, 
(shown  by  the  cross-lines  in  the  figure.)     When  the  bulbs  of 
this  instrument  are  heated  or  cooled  alike,  no  change  is  seen 

.—  ^^  in  the  position  of  the   column,  but  the 

\&  CJ^  instant   any    inequality    of   temperature 

exists  between  them,  as  from  bringing 
the  hand  near  one  of  them,  the  column 
of  fluid  moves  rapidly  over  the  scale.  A 
modification  of  this  instrument,  of  great 
delicacy,  was  contrived  by  Dr.  Howard 
of  Baltimore,  in  which  ether  was  used, 
the  bulbs  being  vacuous  of  air.  It  is 
called  a  differential  thermometer,  be- 
cause it  notes  only  differences  of  tem- 
perature, and  not  actual  temperature. 

81.  Pyrometers. — All  common  thermometers  arc  limited 
to  comparatively  low  temperature*'.     Mercury  boils  at  about 
660°,  above  which  we  can  judge  of  temperatures  only  by  the 
expansion    of   solids.     We    have   thermometers   made  with 
gases  or  vapors,  and  with  fluids,  and  pyrometers  made  with 
solids. 

A  Pyrometer*  is  an  instrument  for  measuring  high  tem- 
peratures. The  only  instrument  of  this  sort  which  we  need 
mention,  as  it  is  the  only  one  susceptible  of  accuracy,  is 
Daniell's  Register  Pyrometer.  It  consists  of  a  hollow  case 
of  black  lead,  or  plumbago,  into  which  is  dropped  a  bar  of  metal, 
(platinum  is  preferable,)  secured  to  its  place  by  a  strap  of 
platinum  and  a  wedge  of  porcelain.  The  whole  is  then 
heated,  as  for  instance,  by  placing  it  in  a  pot  of  molten 

What  the  minimum  ?  80.  What  is  a  differential  thermometer  I 
Why  so  called  T  81.  What  is  a  pyrometer,  and  its  use  ? 

*  From  the  Greek,  pur,  fire,  and  matron,  measure.  A  very  conve- 
nient form  of  pyrometer  for  illustration,  is  made  by  all  instrument- 
makers,  which  shows  the  expansion  of  a  metallic  bar,  heated  by  a 
spirit-lamp,  moving  an  index  like  a  clock-pointer. 


EXPANSION. 


63 


silver,  whose  temperature  wo  wish 
to  ascertain.  The  metal  bar  ex- 
pands mueh  more  than  the  case 
of  black  lead,  and  being  confined 
from  moving  in  any  but  an  up- 
ward direction,  drives  forward  the 
arm  of  a  lever,  as  shown  in  the 
figure,  over  a  graduated  arc,  on 
which  we  read  the  degrees  of  Fah- 
renheit's scale ;  (this  graduation 
has  been  determined  beforehand 
with  great  care.)  This  instrument 
gives  very  accurate  results;  by 
it  the  melting  point  of  cast  iron  has  been  found  to  be 
2786°  F.,  and  of  silver  I8600  F.  The  highest  heat  of  a 
good  wind- furnace,  is  3300°  F. 

Having,  to  a  sufficient  extent,  become  acquainted  with  in- 
struments for  measuring  temperature,  and  with  the  principles 
of  their  construction,  we  can  now  proceed  intelligently  with 
our  main  subject. 

82.  Expansion  of  Solids  and  Liquids. — (1.)  Different 
solids  expand  differently  with  equal  increase  of  temperature. 
(2.)  The  same  solid  expands  equally  for  every  equal  addition 
of  heat  below  212°.     Between  the  freezing  and   boiling  of 
water,  350  cubic  inches  of  lead  become  351 ;  800  of  iron 
become  801 ;  and  1000  of  glass  become  1001.     Each  solid, 
in  fact,  has  a  rate  of  expansion  peculiar  to  itself.     The  same 
is  true  of  liquids.     1000  parts  of  water  between  32°   and 
212°,  expand  to  1046   parts;  and  1000  parts  of  quicksilver 
become   1080  parts.     The  expansions  are  gradual,  both  in 
solids  and   liquids,  and  on  withdrawing  the  heat,  they  return 
with  equal  regularity   to  their   former  dimensions.     Above 
212°,  the  expansion  of  both  solids  and  liquids  becomes  irreg- 
ular and  increases. 

83.  The  unequal  expansion  of  solids  is  well  shown   by 
joining  firmly,  by  rivets,  two  bars,  one  of  iron   and   one   of 
brass,  as  in  the  figure.     When  they  are  heated,  the  brass  ex- 


What  is  the  principle  of  Daniell's  pyrometer  ?  What  are  some 
of  the  results  obtained  by  it  ?  82.  How  do  solids  expand  ?  How 
with  equal  increments  of  heat  ?  Name  some  examples.  Also  some 
of  liquids.  Above  212°  how  do  bodies  expand  ?  83.  How  is  the 
unequal  expansion  of  solids  shown  ? 


64 


HEAT. 


panding  most,  will  cause  the  compound  bar  to  bend,  as  shown 
^—^  ..-.. :.-J-J^L_:_^_I_J _ jL-A-^' .- v  in   the   lower  figure.     If 

they  are  cooled  by  ice,  the 
brass    contracting     most, 
will  bend  the  united  metals 
in  an  opposite  direction. 
84.   The  Compensation  Pendulum  gives  a  beautiful  appli- 
cation of  the  law  of  unequal  expansion  to  regulating  the  rate  of 
„  rx     time-pieces.     The  length  of  the  pendulum 

X  is  altered  by  variations  of  temperature,  and 

, II    _  of  course  the  rate  of  the  clock  is  disturbed. 

A  perfect  compensation  for  this  error  is  ob- 
tained by  the  use  of  a  compound  pendulum  of 
brass  and   iron,  or  other  two  metals,  ar- 
ranged as  is  shown  in  figure  a,  in  such  a 
manner  that  the  expansion  of  one  metal 
downwards  will  exactly  counteract  that  of 
the   other  metal    upwards ;    thus  keeping 
the  ball  of  the  pendulum  at  a  uniform  dis- 
tance from  the  point  of  suspension.     The 
shaded    bars    represent  the  iron,  and    the 
light  ones,  the  brass.     The  same  object  is 
accomplished  by  using  mercury,  as  shown 
in  figure  &,  contained  in  a  glass  or  steel 
vessel   at   the  end   of  the    pendulum-rod. 
The  expansion  which  lengthens  the  rod  also 
increases  the  volume  of  the  mercury ;  this  increase  of  bulk 
in  the  mercury  raises  the  centre  of  gravity  to  an   exactly 
compensating  amount,  and  the  clock   remains  unaltered  in 
rate.     Watches   and    chronometers   are 
regulated  by  a  like  beautiful  contrivance. 
The  balance-wheel  c,  on  whose  uniform 
motion  the  regularity  of  the  watcli  or 
chronometer    depends,    is    liable    to    a 
change  of  dimensions  from  heat  or  cold. 
If  made  smaller,  it  will  move  faster,  and 
if  larger,  slower.     To  avoid   this  error, 
c  the  outside  of  the  wheel  is  made  of  brass, 

the  inside  of  steel,  and  cut  at  two  opposite  points  ;  one  end  of 


84.  How  is  the  unequal   expansion  of  metals  used  in  regulating 
time-pieces  ?    How  is  the  chronometer  balance  constructed  ? 


EXPANSION.  65 

each  part  is  screwed  to  the  arm,  and  the  loose  ends  of  the 
rim,  being  united  by  a  screw,  are  drawn  in  or  thrown  out 
by  the  changes  of  temperature,  in  precise  proportion  to  the 
amount  of  change  ;  thus  perfectly  adapting  the  revolution  of 
the  wheel  to  the  force  of  the  spring.  The  principle  of  this 
wheel  will  be  seen  in  the  compound  bars.  (83.) 

85.  Practical  applications  of  the  laws  of  expansion  in 
solids  are  frequently  made  with  great  advantage  in  the  arts. 
The  rivets  which  hold  together  the  plates  of  iron  in  steam- 
boilers  are  put  in  and  secured  while  red-hot,  and  on  cooling 
draw  together  the  opposite  edges  of  the  plates  with  great 
power.     The  wheel- wright  secures  the  parts  of  a  carriage- 
wheel  by  a  red-hot  tire,  or  belt  of  iron,  which  being  quickly 
quenched,  before  it  chars  the  wood,  binds  the  whole  fabric 
together  with  wonderful   firmness.     The  walls  of  the  Con- 
servatory of  Arts  in  Paris  were  safely  drawn  into  a  vertical 
position  after  they  had  bulged  badly,  by  the  alternate  con- 
traction and  expansion  of  large  rods  of-iron  passed  across  it, 
and  so  secured  by  screw-nuts  and   heated  by  argand  lamps 
as  to  draw  the  walls  inward.     Towers  of  churches  and  other 
buildings  have  been  thrown  down  or  otherwise  injured   by 
the  expansion  of  large  iron   rods,  (anchors,)  built  into  the 
masonry  with  the  design  of  strengthening  them.     The  me- 
chanical arts  are,  in  fact,  full  of  beautiful  applications  of  the 
principles  of  expansion. 

86.  Unequal  Expansion  of  Water. — The  general  law  of 
expansion  for  nearly  all  solids  and  fluids,  especially  within  the 
limits  of  the  freezing  and  boiling  points  of  water,  is,  that  each 
solid  or  fluid  expands  or  contracts  an  equal  amount  for  every 
like  increase  and  reduction  of  temperature,  each  body  having 
its  own  rate  of  alteration  (82.)     There  are,  however,  some 
exceptions  to  this  law,  of  which  water  offers  a  remarkable 
example;  the  comfort,  and  even  habitabilily  of  our  globe,  are 
in  a  great  degree  dependent  on  this  exception  to  the  ordinary 
laws  of  nature.     We  will  briefly  explain  it,  and  the  effects 
resulting  from  it. 

If  we  fill  a  large  thermometer-tube  or  bulbed  glass  (like 
the  one  figured  in  74,  «)  with  water,  and  place  it  in  a  cold 


85.  Name  some  other  practical  applications  of  the  same  principle 
in  the  arts.     86.  Explain  the  unequal  expansion  of  water. 

6* 


66  HEAT. 

situation,*  where  we  can  observe  the  fall  of  the  temperature 
by  the  thermometer,  we  shall  see  the  column  descend  regu- 
larly with  the  temperakire,  until  it  reaches  39°*1  F.,  when 
the  contrary  effect  will  take  place ;  the  water  then  begins 
suddenly  to  rise  in  the  tube,  by  a  regular  expansion,  until  the 
temperature  falls  to  32°,  when  so  sudden  an  expansion  takes 
place  as  to  throw  the  water  in  a  jet  from  the  open  orifice, 
and  the  ball  at  the  same  time  is  not  unfrequently  broken 
from  the  solidification  of  the  water.  If,  on  the  other  hand, 
we  heat  water  in  such  an  apparatus,  commencing  at  32°, 
we  shall  find  that,  until  the  temperature  rises  to  40°,  the 
fluid,  in  place  of  expanding  as  we  might  expect,  will  actually 
contract.  Water  has,  therefore,  its  greatest  density  at  39°'l, 
and  its  density  is  the  same  for  equal  temjxjraturcs  above  and 
below  this  point;  thus  we  shall  find  it  having  a  similar 
density  at  34°  and  45°,  and  this  is  true  until  it  reaches  the 
point  of  solidification  at  32°. 

87.  Beneficial  Results. — Let  us  now  observe  what  useful 
end  this  curious  irregularity  in  the  expansion  of  water  sub- 
serves. When  winter  approaches,  the  lakes  and  rivers,  by  the 
contact  of  the  cold  air,  begin  to  lose  their  heat  on  the  surface ; 
the  colder  water,  being  more  dense,  falls  to  the  bottom,  and 
its  place  is  supplied  by  warmer  water  rising  from  below.  A 
system  of  circulation  is  thus  set  in  motion,  and  its  tendency, 
if  the  mass  of  water  is  not  too  large,  is  to  reduce  the  whole, 
gradually,  to  the  same  temperature  throughout.  When, 
however,  the  water  has  cooled  to  39°*1,  this  circulation  is 
suddenly  stopped  by  the  operation  of  the  law  just  explained  : 
below  this  point  the  water  no  longer  contracts  by  cooling,  and 
of  course  does  not  sink,  but  on  the  contrary  expanding,  as 
before  explained,  it  becomes  relatively  lighter,  and  remains 
on  the  surface ;  the  temperature  of  this  layer  or  upj>cr  stratum 
gradually  falls,  until  the  freezing  point  is  reached  and  a  film 
of  ice  is  formed.  But  as  ice  is  a  very  bad  conductor,  the 
heat  now  escapes  with  extreme  slowness  ;  all  currents  tending 


At  what  temperature  is  it  most  dense  ?  How  is  it  at  equal  tem- 
peratures above  and  below  this  point  ?  87.  Explain  the  use  of  the 
irregular  expansion  of  water  in  its  operation  in  nature.  Why  does 
not  the  heat  of  the  water  escape  after  the  ice  commences  forming  ? 

*  A  freezing  mixture  of  salt  and  ice  surrounding  it  will  answer 
the  purpose  very  well. 


COMMUNICATION   OF    HEAT.  67 

to  convey  away  the  cooler  parts  of  the  water  are  arrested, 
and  the  thickness  of  the  ice  can  increase  only  by  the  slow 
conduction  through  the  film  already  formed  ;  the  consequence 
is,  that  our  most  severe  winters  fail  to  make  ice  of  any  great 
thickness.  Other  causes,  also,  which  we  shall  presently  ex- 
plain, co-operate  at  all  times  to  render  the  freezing  of  water  a 
very  slow  process.  If  this  irregularity  did  not  exist,  there  is 
every  reason  to  believe  that  the  entire  waters  of  the  globe* 
would  freeze  solid :  when  any  portion  reached  the  point  of 
congelation,  all  would  become  solid  at  once,  like  a  mass  of 
molten  metal  cooled  in  a  crucible.  We  cannot  fail  to  be  im- 
pressed by  the  wisdom  of  that  power,  which  not  only  frames 
great  general  laws  for  the  government  of  matter,  but  also 
makes  exceptions  to  them,  when  the  welfare  of  His  creatures 
requires  them. 

88.  The  expansion  of  all  gases  and  vapors  is  the  same 
for  an  equal  degree  of  heat,  and  equal  increments  of  heat 
produce  equal  amounts  of  expansion.  This  rate  of  expan- 
sion is  not  altered  by  any  change  in  the  compression  or  elas- 
tic force  of  the  gas,  and  amounts  to  — J^th  part  of  the  volume 
of  the  gas  at  0°  for  each  degree  of  Fahrenheit's  scale. 

When  gases  are  near  the  point  of  compression  at  which 
they  become  liquid,  this  law  becomes  irregular. 

The  expansion  of  air  by  heat,  is  one  cause  of  winds  and 
atmospheric  currents.  The  trade-winds  and  other  regular 
winds  so  well  known  to  mariners,  are  the  joint  result  of  the 
motion  of  the  earth  on  its  axis,  and  the  rise  of  heated  air 
from  the  equatorial  regions  of  the  globe. 


2.  Communication/of  Heat. — Equilibrium  of  Temperature. 

89.  Equilibrium  of  Temperature. — A  healed  body,  like 
a  red-hot  camion-ball,  cools  when  removed  from  the  source 


What  limits  the  thickness  of  ice  ?  What  might  happen  but  for 
this  ?  88.  What  is  the  law  of  expansion  in  gases  ?  What  irregularity 
does  this  law  undergo  ?  What  results  from  the  expansion  of  atmo- 
spheric air  ?  89.  What  is  equilibrium  of  temperature  ?  Explain 
how  a  hot  body  may  cool.  (1.)  (2.)  (3.) 


*  Sea-water  above  32°  is  not  subject  to  the  exception,  but  it  is 
below  28o. 


68  HEAT. 

of  heat;  (1)  by  communicating  its  heat  to  the  substance 
supporting  it,  (conduction ;)  (2)  by  the  contact  of  the  atmo- 
sphere conveying  it  away,  (convection ;)  and  (3)  by  direct 
radiation,  or  a  transmission  of  rays  of  heat  in  all  directions 
through  the  surrounding  air,  as  light  (52)  is  transmitted. 
All  these  causes  act  to  withdraw  the  excess  of  heat  from  the 
heated  body,  which  thus  divides  itself  equally  among  surround- 
ing bodies  according  to  their  several  powers  of  receiving  it, 
until  a  perfect  equilibrium  of  temperature  is  produced,  the  hot 
body  has  become  cool,  and  the  others  have  gained  heat. 

In  liquids  or  gases,  this  uniform  diffusion  or  distribution  of 
temperature  takes  place  rapidly,  localise  of  the  mobility  of 
their  particles ;  but  in  solids,  much  more  slowly.  Its  dif- 
fusion has  no  connection  with  the  conducting  power  of  the 
fluids,  however,  which  are  among  the  worst  of  conductors. 

90.  Conduction  of  Heat. — Each  solid  has  its  own  pecu- 
liar power  of  conducting  heat,  but  in  all  it  is  a  progressive 
operation,  the  heat  seeming  to  travel  from  particle  to  particle 
with  greater  or  less  rapidity,  according  to  the  conducting 
power  of  the  solid.  If  we  hold  a  pipe-stem  or  glass  rod  in 
the  flame  of  a  spirit-lamp  or  candlo,  wo  can  heat  it  to  red- 
ness within  an  inch  of  our  fingers  with  no  inconvenience ; 
but  a  wire  of  silver  or  copper  would  burn  us  in  a  very  short 
time  when  at  the  distance  of  many  inches  from  the  flame. 
.  ===ii===^= — ==  This  is  owing  to  a 

0       difference    inherent    in 
O      these  solids,  which  we 

call  conducting  power.  The  progress  of  conducted  heat  in 
a  solid  is  easily  shown,  as  in  the  annexed  figure,  representing 
a  rod  of  copper,  to  which  are  stuck  by  wax  several  marbles 
at  equal  distances  ;  one  end  is  held  over  a  lamp,  and  the 
marbles  drop  off,  one  by  one,  as  the  heat  melts  the  wax ; 
that  nearest  the  lamp  falling  first,  and  so  on.  If  the  rod  is 
of  copper,  they  all  drop  very  soon  ;  but  if  a  rod 
of  lead  or  platinum  is  used,  the  heat  is  conveyed 
much  more  slowly.  Little  cones  of  various 
metals,  and  other  substances,  may  be  tipped 


How  does  the  diffusion  of  heat  take  place  in  gases  and  liquids  ? 
How  in  solids  ?  90.  Explain  conduction  in  solids.  What  experi- 
ments are  named  in  illustration  of  it  ? 


COMMUNICATION   OF   HEAT.  69 

with  wax  or  bits  of  phosphorus,*  as  shown  in  the  figure  &, 
and  placed  on  a  hot  surface.  The  wax  will  melt,  or  the  phos- 
phorus inflame,  at  different  times,  according  to  the  conduct- 
ing power  of  the  various  solids.  Accurate  experiments  have 
been  made,  which  have  enabled  us  to  arrange  most  solids  in 
a  table  showing  their  conducting  powers.  The  metals  as 
a  class  are  good  conductors,  while  wood,  charcoal,  fire-clay, 
and  similar  bodies,  are  bad  ones.  Thus  gold  is  the  best 
conductor,  and  may  be  represented  by  the  number  1000  ;  then 
marble  will  be  23-5,  porcelain  12,  and  fire-clay  11.  Metals 
compared  with  each  other  are  very  different  in  conducting 
power.  Thus — 


Gold, 

1000. 

Iron, 

375. 

Silver, 

973. 

Zinc, 

363. 

Copper, 
Platinum, 

898. 
381. 

Tin, 
Lead, 

304. 
180. 

91.  The  sense  of  touch  gives  us  a  good   idea  of  the  dif- 
ferent conducting  power  of  various  solids.     All  the  articles 
in  an  apartment  have  nearly  the  same  temperature ;  but  if 
we  lay  our  hand  on  a  wooden  table,  the  sensation  is  very 
different  from  that  we  feel  on  touching  the  marble  mantel  or 
the  metal  door-knob.     The  carpet  will  give  us  still  a  different 
sensation.     The  marble  feels  cold,  because  it  rapidly  conducts 
away  the  heat  from  the  hand  ;  while  the  carpet,  being  a  very 
bad  conductor,  retains  and  accumulates  the  heat,  and   thus 
feels  warm.     Clothing  is  not  itself  warm,  but  being  a  bad 
conductor  retains  the  heat  of  the  body.     A  film  of  confined 
air  is  one  of  the  worst  conductors ;  loose  clothes  are  therefore 
warmer  than  those  which  fit  closely.     For  the  same  reason, 
porous  bodies,  like  charcoal,  are   bad   conductors ;    and  a 
wooden  handle  enables  us  to  manage  hot  bodies  with  ease. 

92.  The  conducting  power  of  fluids  is  very  small.     This 
is  contrary  to  the  general   impression  of  people,  who  think, 
from  the  ease  with  which  a  tea-kettle  boils,  that  liquids  con- 


How  are  the  different  classes  of  bodies  as  conductors  ?  Name 
some  examples.  Give  some  examples  from  the  table.  91.  Explain 
the  relation  of  our  sense  of  touch  to  the  conducting  power  of  bodies. 


*  If  phosphorus  is  used,  some  screen  must  be  employed  to  cut  off 
the  radiant  heat,  which  will  otherwise  inflame  it  prematurely. 


70 


HEAT. 


duct  heat  with  facility.  A  simple  and  instructive  experiment 
will  prove  to  us  that  the  conducting 
power  of  fluids  is  very  low.  A  glass, 
like  that  in  the  figure,  is  filled  nearly  to 
the  brim  with  water.  A  thermometer- 
lube,  with  a  large  ball,  is  so  arranged 
in  it  that  the  ball  is  just  covered,  and  no 
more,  with  the  water ;  the  stem  passes  out 
at  the  bottom  through  a  tight  cork,  and 
has  a  little  colored  fluid,  L,  in  it,  which 
will  of  course  move  with  any  change  of 
bulk  in  the  air  contained  in  the  ball. 

Thus  arranged,  a  pointer,  I,  marks 
exactly  the  position  of  one  of  the  drops 
of  inclosed  fluid,  and  a  little  ether  is 
poured  on  the  surface  of  the  water,  and 
set  on  fire.  The  flame  is  intensely  hot, 
and  rests  on  the  surface  of  the  water ; 
the  column  of  fluid  at  I  is,  however, 
unmoved,  which  would  not  be  the  case 
if  any  sensible  quantity  of  heat  had 
been  imparted  to  the  water.  The 
warmth  of  the  hand  touching  the  ball 
will  at  once  move  the  fluid  at  I,  by  ex- 
panding the  air  within.  By  heating  a 
vessel  of  water  on  the  top,  then,  we 
should  never  succeed  in  creating  any- 
thing more  than  a  superficial  boiling; 
at  the  depth  of  a  few  inches  the  water  would  remain  cold. 

93.  The  conducting  power  of  gases  is  also  very  small. 
Heat  travels  with  extreme  slowness  through  a  confined  por- 
tion of  air  (91.)  This  is  a  very  different  thing  from  the 
convection  of  heat  in  gases,  which  we  will  presently  explain. 
Double  windows  and  doors,  and  furring  so  called,  of  plas- 
tered walls,  afford  excellent  illustrations  of  the  slow  conduction 
of  heat  through  confined  air.  We  have  no  proof  that  heat 
can  be  conducted  in  any  degree  by  gases  and  vapors.  To 
illustrate  the  relative  conducting  power  of  solids,  fluids,  and 
gases;  if  we  touch  a  rod  of  metal  heated  to  1*20°,  we  shall 


92.  How  is  the  conducting  power  of  fluids  ?  Give  an  experiment- 
al illustration.  93.  How  is  it  in  gases  ?  Give  illustrations. 
What  comparative  trial  in  solids,  fluids,  and  gas,  is  named  ? 


COMMUNICATION  OF  HEAT. 


71 


be  severely  burned;  water  at  150°  will  not  scald  us  if  we 
keep  the  hand  still,  and  the  heat  is  gradually  raised ;  while 
air  at  300°  has  been  often  endured  without  injury.  The 
oven-girls  of  Germany,  clad  in  thick  socks  of  woolen,  to  pro- 
tect the  feet,  enter  ovens  without  inconvenience  where  all 
kinds  of  culinary  operations  are  going  on,  at  a  temperature 
above  300°  ;  although  the  touch  of  any  metallic  article  while 
there  would  severely  burn  them. 

94.  Convection  of  Heat. — Fluids  and  gases  are  heated 
by  what  is  termed  Convection.  Heat  applied  from  beneath 
to  a  vessel  containing  water,  heats 
the  layer  or  film  of  particles  in 
contact  with  the  vessel.  These  ex- 
pand with  the  heat,  and  consequent- 
ly, becoming  lighter,  rise,  and  colder 
particles  supply  their  place,  which 
also  rise  in  turn,  and  so  the  whole 
contents  of  the  vessel  come  succes- 
sively into  contact  with  the  source  of 
heat,  and  convey  it  away.  This  is 
well  illustrated  in  the  annexed  figure, 
which  shows  how  water  acts  in  a 
vessel  of  glass,  when  heated  at  a 
point  beneath  by  a  spirit-lamp.  Each 
particle  in  turn  comes  under  the 
influence  of  heat,  because  of  the  per- 
fect mobility  of  the  fluid,  and  the  heat 
is  thus  conveyed  to,  and  distributed 
throughout,  the  whole  mass.  A 
series  of  such  currents  exist  in  every 
vessel  in  which  water  is  boiled,  and  they  are  rendered  more 
evident,  by  throwing  into  it  a  few  grains  of  some  solid,  (like 
amber,)  so  nearly  of  the  same  gravity  of  water,  that  it  will 
rise  and  fall  with  the  currents.  A  perpetual  circulation  is 
thus  established  in  fluids,  which  serves  to  keep  up  the  equi- 
librium of  temperature  in  our  globe.  \ 
KS95.  In  the  air,  and  in  all  gases  and  vapors,  the  same  thing 
happens.  The  earth  is  heated  by  the  sun's  rays,  and  the 


What  is  said  of  the  oven-girls  in  Germany  ?  94.  How  are  fluids 
and  gases  heated  ?  Explain  what  is  meant  by  convection  of  heat. 
Give  an  account  of  the  experiment. 


72  HEAT. 

film  of  air  resting  on  the  heated  surface  rises,  or  tends  to 
rise,  to  be  replaced  by  colder  air.  The  rarified  air  may  be 
easily  seen  on  a  hot  day,  rising  from  the  surface  of  the  earth, 
being  made  visible  by  its  different  refractive  power.  Hence 
arise  many  aerial  currents  and  winds.  The  currents  of  the 
ocean  are  also  influenced  by  the  same  cause. 

96.  Convection  and  conduction  of  heat  will,  therefore,  be 
carefully  distinguished  from  each  other  by  the  learner.     Heat 
is,  so  to  speak,  transported  rapidly  in   fluids  by  convection, 
while  by  conduction  it  travels  slowly  and  progressively  from 
particle  to  particle,  within  the  limits  of  the  body  subject  to  it. 

97.  Radiant  Heat. — We  have  spoken  of  the  sun's  rays 
as   composed    of  both    light  and  heat ;    these  rays  of  heat 
proceed    from    all    hot   bodies,  at  all   temperatures,  for  the 
slightest  disturbance  of  the  equilibrium  of  temperature  will 
occasion  their  emission.     Radiant  heat  is  subject  in  all  respects 
to  the  same  laws,  and  possesses  the  same  habitudes  as  light. 
It  can  pass  through  many  substances ;  it  is  subject  to  reflec- 
tion, absorption,  refraction,  and  polarization.     Radiation  of 
heat  takes  place  in  a  vacuum  much  more  rapidly  than  in  air, 
and  is,  therefore,  quite  independent  of  any  conducting  me- 
dium. 

98.  Reflection  of  heat  is  shown  by  the  concave  parabolic 
mirror.     All  rays  of  heat  or  light  falling  on  this  form  of  me- 
tallic mirror  are  collected  atF,  the  focus,  and 
a  hot  body  placed  in  the  focus  will  have  its 
rajs  sent  forth  in  parallel  straight  lines,  as 
shown  in  the  figure.     A  second  and  simi- 
lar mirror  may  be  so  placed  as  to  receive 
and  collect  in  a  focus  all  the  rays  proceed- 
ing from  any  body  in  the  focus  of  the  other, 
where  they  will  become  evident  by  their 
effect   on    the  thermometer.      If   the   hot 
body  be  a  red-hot  cannon-toll,  and  the  mir- 
rors are  carefully  adjusted,  so  as  to  be  ex- 
actly opposite  each  other  in  the  same  line,  the  accumulation 
of  heat  in  the  focus  of  the  second  mirror  is  such,  as  to  inflame 
dry  tinder,  or  gunpowder,  even  at  twenty  feet  distance.     This 

95.  Explain  the  origin  of  aerial  and  oceanic  currents.  96.  Con- 
trast the  effects  of  convection  and  conduction.  97.  What  is  radiant 
heat  f  From  what  bodies  does  it  flow,  and  why  ?  What  is  said 
of  its  properties  ?  98.  Explain  the  reflection  of  heat,  and  the  me- 
tallic mirrors. 


COMMUNICATION  OF  HEAT.  73 

arrangement  is  shown  in  the  annexed  figure,  and  the  experi- 
ment is  a  most  strik-  £\ 
ing  and  satisfactory  A  C^ 
one.  It  is  quite  es-  "^ 
sential  that  the  mir- 
rors should  be  highly 
polished  ;  otherwise 
the  heat,  in  place  of 
being  reflected  to  the 
second  mirror,  will  be  absorbed  by  the  dull  surface.  A 
bright  mirror  will  not  become  sensibly  hotter  from  the  near 
approach  of  the  hot  body,  nearly  the  whole  heat  being  re- 
flected;  but  a  black  mirror  will  grow  rapidly  hot,  and  will 
then  emit  heat  itself,  by  what  has  been  called  secondary 
radiation. 

99.  The  formation  of  dew  is  owing  to  radiation,  cooling 
the  surface  of  the  earth  so  rapidly,  that  the  moisture  of  the 
air,  which  is  always  abundant  in  summer,  is  condensed  upon 
it,  as  we  see  it  on  the  outside  of  a  tumbler  of  iced-water  in  a 
hot  day.     Radiation  takes  place  more  rapidly  from  the  sur- 
face of  grass  and  vegetation,  than  from   dry  stones  or  dusty 
roads :  for  this  reason,  plants  receive  abundant  dew,  while  the 
barren  sand  has  none. 

100.  Radiation  of  cold  was  formerly  supposed  to  occur, 
because  a  mass  of  ice  placed  in  the  focus  of  one  mirror, 
caused  the  thermometer  in  the  other  to  fall.     The  true  expla- 
nation of  this  is,  that  the  thermometer,  in  this  case,  is  the  hot 
body,  and  parts  with  heat  to  melt  the  ice,  and  thus  restore  the 
equilibrium  of  temperature.     Cold  is  merely  the  absence  of 
heat,  and  is  a  negative,  and  not  a  positive  quality. 

101.  Absorption  of  Heat. — All  black  and  dull   surfaces 
absorb  heat  very  rapidly  when  exposed  to  its  action,  and  part 
with  it  again  by  secondary  radiation.     The  sun  shining  on  a 
person  dressed  in  black,  is  felt  with  much  more  power  than 
if  he  were  dressed  in  white.     The  former  color  rapidly  ab- 
sorbs heat,  while  from  the  latter  a  considerable  part  of  it  is 
reflected.     The  color  of  bodies  has  nothing  to  do  with  their 
radiating  powers,  and  one  colored  cloth  is  as  warm  in  winter 
as  another,  as  regards  the  emission  of  heat. 


What  experiment  is  shown  by  the  mirrors  ?  What  if  they  are 
dull  or  black  ?  99.  Explain  dew.  100.  Explain  the  supposed  ra- 
diation of  cold.  101.  How  does  color  affect  absorption? 


74-  I1LAT. 

102.  The  nature  of  the  surface  of  bodies  has  the  greatest 
eiTect  on  their  several  powers  of  radiation.     Hot  water   in  a 
bright  tin  canister,  or  a  polished  silver  tea-pot,  will  remain 
hot  very  much  longer  than  in  a  vessel  with  dull  or  roughened 
surfaces.     A  coating  of  lamp-black  on  the  surface  of  a  tin 
canister,  placed  in   the  focus   of  the   mirror,  will  radiate  live 
times  more    heat  from    boiling  water  than    clean  lead,  and 
eight  times  more  than  bright  tin,  as  proved  by  the  differential 
thermometer.     Bright  metals  have  the  lowest  radiating  power, 
and  hence  are  selected  to  preserve  heat  in  those  substances 
which  we  wish  to  keep  hot.     For  the  same  reason,  tlicy  are 
the  worst  vessels  in  which  to  heat  a  fluid.     The  effort  to  boil 
water  in  a  bright  cop|>er  tea-kettle,  is  very  tedious ;  as  soon, 
however,  as  the  surface  becomes  sooty  from  the  lire,  the  heat 
passes  in  rapidly.     The  nature  and  not   the  color  of  the  sur- 
face affects  radiation.     A  dull  cast-iron  stove  radiates   more 
heat  than  a   polished  sheet-iron   one — the  openness  of  the 
pores  and  great  number  of  points  of  the  cast-iron  materially 
aid  its  radiating  power. 

3.   Transmission  of  Heat  through  Bcnlies. 

103.  The  rays  of  heat  from  the  sun,  like  the  rays  of  light 
from  the  same  luminary,  pass  through  transparent  substances 
with  little  change  or  loss.     Radiant  heat,  however,  from  ter- 
restial  sources,  whether  luminous  or  not,  is  in  a  great  mea- 
sure arrested  by  many  transparent  substances.     If  the  sun's 
rays  be  concentrated  by  a  metallic  mirror,  the   heat  accom- 
panying them  is  so  intense  at  the  focus  as  to  fuse  copper  and 
silver  with  ease.     A  pane  of  colorless  window-glass  inter- 
posed between  the   mirror  and  the  focus,  will  not   stop  any 
considerable  part  of  the  heat.     If  the  same  mirror  is  presented 
to  any  other  source  of  heat,  however,  (as  the  red-hot  ball, 
98,)  the  glass  plate  will  stop  nearly  all  the  heat,  although  the 
light   is   undiminished.     We   thus    distinguish   two  sorts  of 
calorific  rays,  which  are  sometimes  called  Solar  and  Culina- 
ry Heat,  and  we  discover  that  substances  transparent  to  light 


Does  it  affect  radiation  ?  102.  What  chiefly  affects  radiating  pow- 
er ?  Give  illustrations.  103.  Give  the  distinction  between  rays  of 
heat  from  the  sun,  and  those  from  most  terrestrial  substances.  How 
are  the  latter  affected  by  glass  and  other  transparent  substances  ? 


TRANSMISSION  OF  HEAT  THROUGH  BODIES.  75 

are  not,  so  to  speak,  transparent  to  heat  in  a  like  degree. 
This  property  is  distinguished  from  transparency  by  the  term 
Diathermancy*  Bodies  allowing  the  passage  of  the  heat 
are  said  to  be  diathcrmous,  while  those  allowing  the  passage 
of  light  are  said  to  1x3  diaphanous.^  Bodies  which  complete- 
ly arrest  the  passage  of  radiant  heat  are  said  to  be  adiather- 
mous. 

Bodies  which  are  highly  transparent  or  diaphanous,  are 
often  completely  adiathermous,  so  that  the  transparency  of  a 
body  is  not  connected  with  its  diathermancy. 

Thus  glass  of  various  sorts  arrests  from  47  per  cent,  to 
67  per  cent,  of  the  rays  of  heat,  while  common  alum  in  per- 
fectly clear  masses  allows  the  passage  of  only  9  rays  in 
100.  On  the  other  hand,  rock-salt  stops  only  8  rays  in  100, 
92  passing  freely  through.  These  facts  are  easily  shown, 
when  no  other  means  are  at  hand,  by  placing  a  tablet  of 
rock-salt  and  one  of  glass  in  a  situation  to  be  exposed  to  the 
heat  of  a  fire.  The  glass  will  soon  grow  so  hot  as  to  burn 
the  fingers,  from  the  quantity  of  heat  arrested  by  it,  while 
the  salt  will  hardly  be  affected.  A  large  air-thermometer,  or 
a  delicate  differential  one,  with  one  ball  blackened,  will  also 
answer  to  make  many  of  these  changes  of  temperature 
evident,  in  the  absence  of  the  more  delicate  means  explained 
in  the  next  section. 

104.  Mellani's  Apparatus. — Nearly  all  the  knowledge  we 
possess  on  this  interesting  branch  of  science,  we  owe  to  the 
labors  of  a  distinguished  Italian  philosopher,  M.  Melloni,  who 
has  invented  a  most  beautiful  apparatus,  by  which  all  these 
observations  and  discoveries  have  been  made.  Its  general 
arrangement  is  represented  in  the  annexed  figure.  The 
degree  of  heat  is  measured  in  this  instrument,  not  by  a  ther- 
mometer, (which  would  be  altogether  too  rude  an  indicator 
of  such  minute  changes  of  temperature  as  are  here  shown,) 


What  is  Diathermancy  ?  What  is  meant  by  diaphanous  ?  What 
by  adiathermous  ?  Are  these  properties  united  generally  ?  Give 
instances. 


*  From  the  Greek,  dia,  through,  and  thermos,  heat,  in  allusion  to 
the  passage  of  heat  through  substances. 

f  From  the  Greek,  dia,  through,  and  phaino,  to  shine. 


76  HEAT. 


but  by  what  is  called  a  tker mo-multiplier,  or  multiplier  of 
heat.  This  is  an  arrangement  of  little  bars  of  the  two  metals, 
antimony  and  bismuth,  about  fifty  of  which  are  soldered 
together  by  their  alternate  ends,  the  whole  being  with  its 
case  not  more  than  2^  inches  long,  by  J  to  ^  of  nn  inch  in 
diameter.  The  least  difference  of  heat  between  the  opposite 
ends  of  this  little  buttery  will  produce  an  electrical  current 
capable  of  influencing  a  magnetic  needle,  in  an  instrument 
called  a  galvanometer.  The  needle  of  the  galvanometer  will 
move  in  exact  accordance  to  the  intensity  of  the  heat.  This 
is  so  delicate  an  instrument,  that  the  radiant  heat  of  the  hand 
held  near  the  battery  will  cause  the  needle  to  move  some  10° 
over  its  graduated  circle.  In  the  figure,  a  is  the  source  of 
heat,  (an  oil-lamp  in  this  case,)  b  a  screen  having  a  hole  to 
admit  the  passage  of  a  bundle  of  rays ;  c  is  the  substance  on 
which  the  heat  is  to  fall ;  d  the  thermo- multiplier,  or  battery, 
which  is  to  receive  the  rays  after  they  have  passed  through 
the  substance  c.  Two  wires  connect  the  opposite  members 
of  this  battery  with  the  galvanometer  *>,  which,  for  steadiness, 
is  placed  on  a  bracket  attached  to  the  wall.  Thus  arranged, 
and  with  various  delicate  aids  which  we  cannot  now  explain, 
a  vast  number  of  most  instructive  experiments  have  been 
made  on  radiant  heat  from  different  sources,  and  its  effect 
ascertained  on  various  substances.  Four  different  sources  of 
heat  were  employed:  (1)  the  naked  flame  of  an  oil-lamp;  (~) 
a  coil  of  platinum  wire  heated  to  redness  by  an  alcohol-lamp  ; 
(3)  a  surface  of  blackened  copper  heated  to  734°,  and  (4,) 
the  same  heated  to  212°  by  boiling  water.  The  first  two 
of  these  are  luminous  sources  of  heat,  the  last  two  not  so. 


104.  Explain  Melloni's  apparatus  from  the  figure.     What  sources 
of  heat  were  used  ? 


TRANSMISSION  OF  HEAT  THROUGH  BODIES. 


77 


The  following  table  will  show  a  few  of  the  principal  re- 
sults. 


Transmission  of  100 

rays  of  heat  from 

Names   of  interposed   substances,  common 

c. 

g 

*S 

a 

« 

thickness,  0-102. 

J3 

•^  e 

•S'S 

|i 

ll 

t 

O 

«•& 

u 

0 

Rock-salt,  transparent  and  colorless,    .     . 

92 

92 

92 

92 

36 

98 

6 

0 

39 

914 

r> 

0 

Rock-crystal             • 

38 

28 

6 

0 

Rock-crystal,  brown,      

37 

28 

6 

0 

g 

2 

o 

o 

8 

0 

0 

0 

Ice,  pure  and  transparent,     

6 

0 

0 

0 

Thus  it  appears  that  rock-salt  is  the  only  substance  which 
permits  an  equal  amount  of  heat  from  all  sources  to  pass. 
In  other  cases  the  number  of  rays  passing  seem  proportioned 
to  the  intensity  of  the  source.  M.  Melloni  has  called  rock- 
salt  the  glass  of  heat,  as  it  permits  heat  to  pass  with  the  same 
ease  that  glass  does  light.  It  is  supposed  that  the  difference 
found  by  experiment  in  the  diathermancy  of  bodies,  is  owing 
to  a  peculiar  relation  which  the  various  rays  of  heat  sustain 
to  these  bodies,  exactly  analogous  to  that  difference  in  the 
rays  of  light  which  we  call  color.  Thus  all  other  bodies, 
except  salt,  act  on  heat  as  colored  glasses  act  on  light, 
entirely  absorbing  some  of  the  colors,  and  allowing  others  to 
pass.  Thus  rock-salt  may  be  said  to  be  colorless  as  respects 
heat,  while  alum  and  ice  are  in  the  same  sense  almost  black. 
Opake  bodies,  like  wood  and  metals,  entirely  prevent  the 
transmission  of  heat ;  but  dark-colored  crystal  is  seen,  by 
the  table,  to  differ  only  1  from  white  crystal,  and  even  per- 
fectly black  glass  does  not  entirely  stop  all  heat. 

105.  By  cutting  rock-salt  into  prisms  and  lenses,  the  heat 
from  radiant  bodies  may  be  reflected,  refracted,  and  concen- 
trated, like  light,  and  doubly  refracting  minerals,  like  Iceland- 
spar,  will  polarize  it.  All  these  interesting  results,  however, 
we  must  pass  without  further  notice. 

Give  some  illustrations  of  the  results  from  the  table.  What  has 
rock-salt  been  called,  and  why  ?  To  what  are  the  different  powers 
of  bodies  in  this  respect  supposed  to  be  owing  ?  105.  What  other 
attributes  of  light  have  been  discovered  in  radiant  heat,  and  how'/ 


78  HEAT. 

4.  Specific  Heat. — Capacity  of  Bodies  for  Heat.      )C 

106.  Specific    heat   is  that   amount  of  heat  require/ to 
raise  any  body  through  a  given  number  of  degrees  of  tem- 
perature, as,  c.  g.,  10°.     It  is  a  remarkable  fact,  and  one  of 
great  importance,  that  the  same  quantity  of  heat  cannot  raise 
different  bodies  through  an  equal  number  of  degrees  of  tem- 
perature.    If  equal  measures  (say  a  pint)  of  mercury  and 
water  be  exposed  to  the  same  source  of  heat,  we  shall  find 
that   the   mercury  will   attain  its  highest  temperature  about 
Twice  as  soon  as  the  water  ;  and  on  removal  from  the  fire,  it 
will  cool   in   half  the  time.     If  a  pint  measure  of  water  at 
150°  be  mixed  quickly  with  an  equal  measure  of  the  same 
fluid  at  50°,  the  two  measures  of  fluid  will  have  the  tempera- 
ture of  100°,  or  the  arithmetical   mean   of  the  two  tempera- 
tures before  mixture.     If,  however,  we  take  one  measure  of 
water  at  150°,  and  an  equal  measure  of  mercury  at  50°,  and 
rapidly  mix    them,  we    shall    find   that   they  will  have  the 
temperature  of  118°.     The  mercury  has  gained  68°,  and  the 
water  lost  only  3*2°,  or  about  half  as  much.     Hence  we  infer 
that  the  same  quantity  of  heat  can   raise  the  temperature  of 
mercury  through  twice  as   many  degrees   as  that  of  water. 
We  thus  prove,  by  actual  trial,  that  each  body  (solid,  fluid, 
or  gas)  has  its  own  relation  to  the  amount  of  heat  required 
to  raise  it  a  given  number  of  degrees  of  heat,  and  this  amount 
being  peculiar  to  each  body,  is  called  its  specific  heat.     As 
water  is  adopted  as  the  standard  of  comparison  for  specific 
heats,  the  specific  heat  of  mercury  will  be  to  water  as  32  to 
68,  or  nearly  0-47.     It  is  more  convenient  to  compare  bodies 
by  weight  than  by  measure  ;   and   hence  if  we   divide  the 
specific    heat  by  measure  (0'47)  by  the  specific  gravity  of 
mercury,  (13-5,)  we  obtain  the   number,  0*035,  its  specific 
heat,  by  a  comparison  of  weights.     The    process   just    de- 
scri!)od  for  determining  specific  heat,  is  called  the  method  of 
mixtures. 

107.  The  method  of  mixtures  can  te  used  to  obtain  the 
specific  heat  of  solids  as  well  as  fluids.     Thus  a  bar  of  cop- 
per of  a  pound  weight  may  be  heated  to  a  temperature  of 
400°,  and  then  put  into  a  pound  of  water  at  50°;  when  the 


106.  What  is  specific  boat  ?  Illustrate  this  in  the  case  of  mercury 
and  water.  Give  tho  specific  heat  of  mercury  by  measure  and 
weight.  What  is  this  method  called  ? 


CHANGES  PRODUCED  BY  HEAT. 


79 


equilibrium  is  restored,  both  will  have  the  temperature  of  72°. 
The  copper  has  lost  228°,  and  the  water  has  gained  22°. 
The  specific  heats  being  then  as  228  :  22,  that  of  the  copper 
is  found  to  be  ^3%  =0-095.  Other  methods  have  been  used 
to  determine  specific  heats,  but  it  is  foreign  to  our  present 
purpose  to  describe  them.  The  following  table  will  show  the 
specific  heats  of  a  number  of  substances : 


Water, 

1-000 

Copper, 

0-095 

Ether, 

0-520 

Lead, 

0-031 

Alcohol, 

0-660 

Gold, 

0-032 

Sulphuric  Acid  0-333 

Antimony, 

0-0/51 

Mercury, 

0-033 

Tin, 

0-056 

Silver, 

0-057 

Phosphorus, 

0-118 

Zinc, 

0-095 

Glass, 

0-197 

Iron, 

0-114 

Lime, 

0-205 

The  specific  heat  is  found  to  be  most  intimately  connected 
with  the  chemical  character  of  the  substance,  and  many  curi- 
ous and  important  inferences  have  been  made  from  the  study 
of  these  relations.  We  shall  have  occasion  to  refer  to  this 
subject  again,  in^  the  chapter  on  Chemical  Philosophy. 

5.  Changes  produced  by  Heat  in  the  state  of  Bodies. 

108.  Liquefaction. — The  change  of  a  solid  to  a  fluid  is 
called  liquefaction,  and  is  always  attended  by  a  remarkable 
absorption  of  heat.  Water  is  a  substance  familiarly  known 
under  all  three  states  of  solid,  fluid,  and  gaseous  ;  and  the 
melting  of  ice  will  furnish  us  a  good  instance  of  the  pheno- 
mena which  take  place  in  the  process  of  liquefaction.  We 
have  already  seen  that  two  equal  measures  of  water  at  diffe- 
rent temperatures  have,  when  mingled,  a  temperature  which 
is  the  mean  of  their  previous  temperatures,  (106.)  If,  how- 
ever, we  take  a  pound  of  ice  (solid  water)  at  32°,  and  a 
pound  of  water  at  212°,  we  shall  find,  when  the  ice  is  melted, 
that  the  two  pounds  of  water  have  the  temperature  of  only 
52°  ;  the  ice  gains  only  20°,  while  the  water  has  lost  160°. 
There  are,  then,  140°  of  heat  lost  in  producing  this  change. 
We  can  take  another  mode  of  trial.  Let  us  expose  a  pound 


107.  Is  it  used  for  solids,  and  how  ?  Give  some  examples  from 
table.  108.  What  is  liquefaction  ?  Explain  and  illustrate  the  change 
of  ice  to  water. 


80  HEAT. 

of  ice  at  32°,  and  another  pound  of  water  at  the  same  tempe- 
rature, to  a  constant  source  of  heat,  in  two  vessels  every  way 
alike,  and  note  the  changes  of  temj)erature  by  the  thermome- 
ter. When  the  ice  is  all  melted,  we  shall  find  that  the  water 
into  which  it  is  converted  has  still  only  the  temperature  of  32°, 
while  the  other  pound  of  water  has  risen  from  3:2°  to  172°  ; 
here  again  we  see  the  loss  of  140°  of  heat  used  in  converting 
the  ice  into  water.  We  may  reverse  the  last  experiment, 
and  lake  equal  weights  of  ice  at  32°  and  water  at  172°,  and 
mix  them  ;  the  ice  will  soon  be  all  melted,  and  the  mixture 
will  have  the  temperature  of  only  32°  :  so  that,  in  whatever 
way  we  may  make  the  trial,  we  constantly  observe  the  loss 
of  140°  of  heat.  This  is  called  the  heat  of  fluidity,  it  being 
necessary  to  the  existence  of  the  water  in  a  fluid  state,  and  it 
is  also  designated  latent  heat,  because  it  is  lost,  absorbed,  or 
concealed,  as  it  were,  and  no  indication  of  it  can  be  found  by 
the  thermometer. 

109.  Congelation. — If  a  vessel  filled  with  water  at  52° 
be  placed  in  an  atmosphere  of  32°,  it  will  rapidly  cool  down 
to  32°  by  the  loss  of  20°  of  temperature.  After  this,  it  will, 
as  may  be  seen  by  the  thermometer,  remain  at  32°,  until  it  is 
all  converted  to  solid  ice ;  although  we  cannot  doubt  that 
it  is  all  the  while  giving  out  a  quantity  of  heat,  which  had 
before  been  insensible  or  latent.  If  the  water  had  been  ten 
minutes  in  cooling  from  52°  to  32°,  (or  in  losing  20°,)  then 
it  would  require  one  hour  and  ten  minutes,  or  seven  times  as 
long,  for  it  to  become  completely  frozen.  If,  then,  in  equal 
times  it  lost  equal  degrees  of  heat,  its  latent  heat  will  be  20° 
X  7=140°,  which  is  the  same  result  as  before. 

Thus  it  is  by  a  wise  order  of  Providence  that  the  freezing 
and  thawing  of  snow  and  ice  are  extremely  slow  and  grad- 
ual processes.  If  water  became  solid  at  once  on  reaching 
32°,  the  water  would  be  suddenly  frozen  to  a  great  depth ; 
and  if  ice  melted  as  quickly  on  reaching  the  same  tempera- 
ture, the  most  sudden  and  dreadful  floods  would  accompany 
these  events,  and  the  common  changes  of  the  seasons  would 
be  calamitous  to  human  comfort  and  life. 


What  amount  of  heat  is  in  all  these  cases  unaccounted  for  ?  What 
is  this  lost  heat  called  ?  What  becomes  of  it  ?  109.  State  the  phe- 
nomena observed  in  freezing.  How  do  we  then  discover  the  same 
quantity  of  latent  heat  in  water  ?  What  reflection  is  hence  drawn 
in  the  order  of  Providence  ? 


LIQUEFACTION.  81 

110.  Freezing  is  a  warming  process. — Water  may  bo 
cooled  below  its  freezing  point  and  still  remain  liquid,  if  its 
surface  be  covered  with  a  thin  film  of  oil,  and  if  it  is  in  a  thin 
smooth  vessel,  kept  quite  still ;  but  the  least  disturbance  will 
cause  it,  when  in  this  situation,  to  become  solid  at  once,  and 
the  temperature  will  immediately  rise  from  23°  or  24°  to  32°. 
The  freezing  of  a  part  has  therefore  given  out  heat  enough  to 
raise  the  temperature  of  the  whole  from  24°  to  32°,  or  through 
8°.     In  like  manner,  it  is  true  that  melting  is  a  cooling  pro- 
cess, although  it  seems  paradoxical  to  say  so.     A  solid  can 
melt  (become  liquid)  only  by  absorbing  heat  from  surround- 
ing bodies,  which  must,  of  course,  become  cooler.     Hence 
in  part  the  cooling  influence  of  an  iceberg,  which  is  often  felt 
for  many  leagues,  or  of  a  large  body  of  snow  on  a  distant 
mountain. 

111.  Freezing  mixtures,  or  the  means  used  to  produce 
artificial  cold,  owe  their  powers  to  the  principles  just   ex- 
plained.    Ice-cream    is    frozen   by    a   mixture   of    snow  or 
pounded  ice  with  common  salt.     In  this  case  the  two  solids 
are   rapidly  changed    to   fluids ;    the   ice  is   melted   by  the 
salt,  and  the  salt  is  dissolved  by  the  water  from  the  melting 
ice.     Both  these  operations  absorb  (or  render  latent)  a  large 
quantity  of  heat.     The  surrounding  bodies  are  called  on  to 
supply  the  heat  required,  and  the  cream,  in  a  thin  metallic 
vessel,  loses  heat  so  rapidly  from  this  cause,  as  to  be  soon 
turned  to  ice.     The  thermometer  will  fall  in  this  operation 
to   0°    F. ;    and  this  was   the   very   experiment   by    whichf 
Fahrenheit  (78)  assumed  that  he  had  attained  to  a  true  zero 
of  cold. 

Nitrate  of  ammonia  dissolved  in  water  at  46°  will  sink 
the  temperature  to  zero,  and  the  exterior  of  the  vessel  be- 
comes at  once  thickly  covered  with  hoar-frost.  Common 
saltpetre,  (nitrate  of  potassa,)  dissolved  in  water,  lowers  its 
temperature  several  degrees,  and  is  therefore  much  used  in 
the  hot  regions  of  Asia,  where  it  abounds,  for  cooling  wine. 
Mercury  may  be  frozen  by  using  a  mixture  of  three  parts  of 
chloride  of  calcium,  and  two  of  dry  snow ;  this  mixture  will 
sink  the  temperature  from  +32°  to  —50°.  It  should  be  di- 
vided into  two  pretty  abundant  portions ;  the  first  of  which 


110.  How  is  freezing  a  warming  process  ?  Illustrate  this.  Why 
is  melting  a  cooling  process?  111.  What  are  freezing  mixtures? 
To  what  do  they  owe  their  power  ?  Give  some  examples. 


82 


HEAT. 


serves  to  cool  down  the  mercury,  and  the  second  is  used 
when  the  first  is  exhausted,  and  completes  the  work. 

But  all  other  means  of  producing  cold  are  insignificant, 

when  compared  to  the  power  of  solidified  carbonic  acid  gas, 

in  a  vacuum,  by  means  of  which,  Dr.  Faraday  has  succeeded 

in  obtaining  a  temperature  of  —175°  below  zero  of  Fahren- 

,    heit's  thermometer. 

\/112.  The  melting  point  of  every  substance  is  very  uni- 
/  fo*m,  and  each  body  has  its  own,  which  is  often  one  of  its 
/  most  characteristic  marks.  Thus  it  is  the  melting  of  ice, 
and  not  the  freezing  of  water,  that  gives  the  constant  tempera- 
ture of  32°.  By  no  contrivance  can  we  raise  the  tempera- 
ture of  ice  above  32°  ;  nor  can  any  other  solid  be  heated  above 
its  melting  point  and  remain  a  solid.  Some  substances,  in 
melting,  pass  at  once,  like  ice,  to  a  state  of  perfect  fluidity  ; 
others  have  an  intermediate  pasty  state.  The  following  table 
contains  the  melting  points  of  a  few  bodies  at  both  ends  of 
the  scale : 


Mercury,           —  39C 
Potassium,       -f  13G 
Newton's  Alloy,212 
Tin,                       412 
Lead,                     612 

Zinc,                      773° 
Silver,                   1873 
Gold,                   2016 
Cast  Iron,            2786 
Platina,  (above)  3280 

113.  Diminution  of  volume  in  a  body  will  cause  a  por- 
tion of  the  latent  heat  to  become  sensible.  Thus,  numerous 
blows  will  condense  iron  or  gold,  and  so  much  heat  will  be 
evolved,  that  blacksmiths  in  this  way  sometimes  kindle  their 
fires.  Water  poured  on  quicklime  combines  with  it,  with 
the  escape  of  much  heat ;  the  water  in  this  case  taking  on 
the  solid  form.  Sulphuric  acid  and  water,  when  mingled, 
give  out  great  heat,  and  the  bulk  of  the  mixture  is  less  than 
that  of  the  two  before  mixing.  Liquefaction  is  always  a 
cooling  process,  and  solidification  a  heating  one,  to  all  sur- 
rounding bodies.  A  certain  quantity  of  heat  may  be  consi- 
dered as  necessary  to  preserve  each  body  in  its  natural  con- 
dition :  if  it  be  condensed,  less  is  required,  and  it  gives  out 

What  is  the  greatest  cold  thus  produced  ?  112.  What  is  said  of 
the  melting  points  ?  Name  some  examples  of  extremes  from  the 
table.  113.  How  does  diminution  of  volume  affect  the  latent  heat 
of  bodies  ?  Name  some  examples. 


VAPORIZATION.  83 

the  excess;  and  if  expanded,  it  absorbs  more.  Dr.  Black, 
of  Scotland,  was  the  first  who  made  known  to  us  the  beau- 
tiful philosophy  of  latent  heat,  and  the  phenomena  of  lique 
faction  and  vaporization. 

114.  Difference  between    heat   and   temperature. — It    is 
easy  to  see,  from  what   has   been  said,  that   the  thermometer 
cannot  tell  us  any  thing  of  the  amount  of  heat  in  a  body,  since 
the  latent  heat  is  quite  insensible  to  any  thcrmometrical   test. 
We  speak  more   properly,  then,  when  we  say  that  we  know  ' 
the  temperature  of  a  body,  than  to  say  we  know  its  heat. 

6.    Vaporization. —  The  boiling  points  of  Bodies. 

115.  A  continuance  of  the  heat  which  melted  the  ice  (1 08) 
into  water,  will   turn   the   water  into  vapor  or  steam.     The 
phenomena  which  attend  this   physical   change  are  not  less 
curious  or  instructive  than  the  last. 

If  we  place  a  known  quantity  of  water  over  a  steady  source 
of  heat,  we  shall  see  the  thermometer  indicating  each  mo- 
ment a  higher  temperature,  until,  at  212°,  the  fluid  boils  ; 
after  which,  the  thermometer  indicates  no  further  change, 
but  remains  steadily  at  the  same  point  until  all  the  water  is 
boiled  away.  Let  us  suppose  that,  at  the  commencement 
of  the  experiment,  the  temperature  of  the  water  was  02°,  and 
that  it  boiled  in  six  minutes  after  it  was  first  exposed  to  the 
heat :  then  the  quantity  of  heat  which  entered  into  it  each 
minute  was  25°,  because  212°,  the  boiling  point,  less  62°, 
leaves  150°  of  heat  accumulated  in  six  minutes,  or  25°  each 
minute.  Now  if  the  source  of  heat  continue  uniform,  we 
shall  find  that  in  forty  minutes  all  the  water  will  be  boiled 
away ;  and  hence  there  must  have  flowed  into  the  water,  to 
convert  it  into  steam,  25°  X  40=1000°.  One  thousand 
degrees  of  heat,  therefore,  have  been  absorbed  in  the  process, 
and  this  constitutes  the  latent  heat  of  steam.  What  we  have 
already  said  on  the  latent  heat  of  liquids  will  render  this  more 
clear.  So  much  heat  was  imparted  to  the  water,  that  if  it 
had  been  a  fixed  solid,  it  would  have  been  heated  to  red- 
ness ;  and  yet  the  steam  from  it,  and  the  fluid  itself,  had 
during  the  whole  time  only  a  temperature  of  212°. 

Who  first  made  known  these  laws?  114.  Distinguish  between 
heat  and  temperature.  115.  What  takes  place  when  we  heat  water  ? 
Explain  the  process  and  the  amount  of  heat  absorbed  by  boiling 
water  ?  What  do  you  call  this  heat  ? 


84  HEAT. 

116.  The  large  amount  of  latent  heat  contained  by  steam, 
becomes  again  sensible  on  its  condensation  to  water.  This 
enables  us  to  make  great  use  of  steam  as  a  means  of  con- 
veying heat.  The  steam  takes  up  a  large  quantity  of  heat, 
and  transports  it  to  the  point  where  we  wish  it  applied. 
gallon  of  water  converted  into  steam,  at  the  ordinary  pressure 
of  the  atmosphere,  will  raise  five  gallons  and  a  half  of  ice- 
cold  water  to  the  boiling  point.  In  this  way  we  can  boil 
water  in  wooden  tanks,  heat  large  buildings  by  steam-pipes, 
and  make  numberless  other  useful  applications  of  steam-heat 
in  the  arts. 

117.  The  distillation  of  water  (or  any  other  fluid)  affords 
a  good   illustration  of  the  quantity  of  latent   heat  conveyed 
away  in  the  vapor.     In  the  arrangement  here  figured,  a  glass 
retort  (R)  is  made  to   contain  a  quantity  of  water,  which  is 
boiled  by  a  lamp  below,  the  steam  is  conveyed  by   the  bent 

neck  to  a  receiving-vessel, 
in  which  it  is  condensed, 
being  surrounded  by  cold 
water  or  ice  poured  into 
the  dish  placed  to  support 
it.  After  the  water  boils 
in  the  retort,  its  tempera- 
ture docs  not  rise  any 
further,  but  the  vapor  con- 
veys the  heat  of  the  lamp 
over  to  the  condenser.  The 
water  which  surrounds  it 
will  grow  rapidly  hot  from 
the  latent  heat  of  the  steam, 
rendered  sensible  by  its 
reconversion  into  water. 
For  this  reason  the  condensing  water  must  be  frequently 
changed.  In  metallic  stills,  the  condenser  is  a  long  metallic 
tube,  bent  into  a  spiral,  (called  a  worm,)  and  surrounded  by 
cold  water. 

118.  The  latent  heat  of  steam,  which  may  be  set  down  at 
about  1000°,  (although  it  is  stated  more  accurately  at  967°,) 


116.  How  does  the  latent  heat  of  steam  again  become  sensible? 
How  much  ice-cold  water  will  one  gallon  turned  to  steam  boil  ? 
117.  How  does  the  process  of  distillation  illustrate  this  ?  118.  How 
does  the  latent  heat  of  steam  compare  with  that  of  the  vapor  of 
other  fluids  ? 


VAPORIZATION.  85 

is  greater  than  that  of  any  other  known  fluid.  The  latent 
heat  of  fluids  has  no  connection  with  their  boiling  point ;  since 
many  liquids  which  boil  at  high  temperatures  have  little 
latent  heat,  and  the  reverse.  The  annexed  table  shows  the 
boiling  points  and  latent  heat  of  the  vapor  of  several  common 
liquids. 


Liquids. 

Boiling  Point. 

Latent  Heat  of  Vapor. 

Water, 
Alcohol, 
Ether, 
Petroleum, 
Oil  of  Turpentine, 
Nitric  Acid,  (strong,) 
Ammonia,*  (liquid,) 

212° 
172 
96 
320 
314 
248 
140 

967° 
442 
302 
178 
178 
532 
837 

119.  Boiling  or  Ebullition  takes  place  in  a  liquid  when 
it  becomes  so  hot  that  its  vapor  can  rise  in  bubbles  to  the  sur- 
face, and  escape  uncondensed  by  the  atmospheric  pressure, 
or  the  temperature  of  the  fluid.  The  elasticity  (or  tension) 
of  the  vapor  then  becomes  greater  than  the  united  pressure  of 
the  fluid  and  the  air.  When  the  boiling  is  vigorous,  a  great 
number  of  these  bubbles  of  uncondensed  vapor  rise  to  the 
surface  at  the  same  instant,  and  the  liquid  is  thrown  into 
violent  agitation.  If  a  vessel  containing  cold  water  be  heated 
suddenly,  the  lower  surface  receives  the  most  heat ;  bubbles 
of  vapor  are  formed,  and  rise  a  little  way,  when,  meeting  the 
colder  water,  the  vapor  is  at  once  condensed,  and  the  liquid, 
before  sustained  by  the  elastic  vapor,  falls  with  a  sudden  jar 
on  the  bottom  of  the  vessel,  producing  a  series  of  little  ex- 
plosions. This  may  be  well  seen  in  a  glass  flask  suddenly 
heated  by  a  lamp.  When  the  heat  is  gradually  applied,  it  is 
so  evenly  and  quietly  distributed  that  this  effect  is  not  per- 
ceived. 

The  boiling  point  is  much  affected  by  the  nature  of  the 
vessel.  In  a  metallic  vessel,  water  boils  at  210°  and  211°. 
If  a  glass  vessel  be  coated  inside  with  shellac,  water  boils  in 
it  at  211°;  but  if  it  be  thoroughly  cleaned  with  sulphuric 


Is  latent  heat  connected  with  the  boiling  point  ?  Illustrate  this 
from  the  table.  119.  What  is  boiling  ?  Illustrate  this.  How  does 
the  nature  of  the  vessel  affect  it  ? 


*  Specific  Gravity,  0-945. 


86  HEAT. 

acid,  it  may  be  heated  to  221°  or  more,  without  the  escape 
of  bubbles.  A  few  grains  of  sand,  or  a  little  fragment  of 
wire,  or  a  small  piece  of  charcoal,  will,  however,  at  once 
equalize  these  differences,  and  cause  the  water  to  boil  quietly 
at  212°.  This  simple  means  will  prevent  the  unpleasant  jar 
from  sudden  escape  of  vapor,  and  frequent  fracture  of  the 
glass  vessel. 

120.  The  pressure  of  the  atmosphere  determines  the  boil- 
ing point  of  fluids ;  and  when  we  speak  of  the  boiling  point, 
we  always  mean  ebullition  under  the  ordinary  pressure  of  the 
air,  or  30  inches  of  the  barometer,  (33.)     It  follows,  there- 
fore, that  by  a  diminution  of  pressure,  water  may  be  made 
to  boil  at  a  much  lower  temperature  than  212°.     In  ascend- 
ing high  mountains,  the  boiling  point  falls  with  the  elevation, 
from  the  diminished  pressure  of  the  air.     On  this  account,  a 
difficulty  is  experienced  at  the  Hospital  of  Saint  Bernard,  on 
the  Swiss  Alps,  in  cooking  eggs  and  other  viands  in  boiling 
water.     This    place  is  8400  feet  above  the  sea,  and  water 
boils  there  at  196°  ;  on  the  summit  of  Mount  Blanc,  it  boils 
at  187°.     We  see  that  it  is  the  temperature,  and  not  the  boil- 
ing which  performs  the  cooking.     The  Rev.  Dr.  Wollaston 
contrived  an  instrument  to  determine  the  height  of  mountains 
by  the  boiling  point.     lie  found  an  ascent  of  530  feet  to  be 
equal  to  a  decrease  of  1°  in  the   boiling  point ;  and  with  a 
thermometer  having  large  spaces,  accurately  subdivided,  T^^ 
of  a  degree  may  be  read.  -^ 

121.  Boiling  under  Diminished  Pressure. — An  experi- 
ment easily  performed,  gives  a  very  good  illustration  of  the  I 
phenomena  of  boiling  under  diminished  pressure.     A  small 
quantity  of  water  is  boiled  in  a  glass  retort,  or  in  a  bolt-head, 
like  that  in  the  following  figure  ;  when  the  water  has  boiled 

a  short  time,  a  good  cork,  previously  well  fitted  to  the  orifice, 
is  firmly  inserted,  and  the  vessel  removed  from  the  heat.  It 
may  now  be  supported  in  an  inverted  position,  with  the  mouth 
under  water,  as  seen  in  the  annexed  figure.  The  boiling 
will  still  continue,  and  more  rapidly  than  before ;  and  if  we 
attempt  to  check  it  by  cold  water  poured  on  the  ball,  we  shall 
only  cause  it  to  boil  more  vehemently.  A  little  hot  water 

120.  What  influences  the  boiling  point  ?  Mention  the  boiling  point 
of  water  on  Mount  Blanc,  and  the  elevation  necessary  to  produce  1° 
of  difference  in  the  boiling  point.  121.  Explain  the  experiment  of 
Dolling  under  diminished  pressure. 


VAPORIZATION. 


87 


will,  however,  at  once  arrest  the  ebullition  of  the  confined 
fluid.  In  this  case,  the  air  is  driven  out  of  the  vessel  on 
the  first  boiling  of  the  water,  and  as  we  close  the  orifice, 
while  the  steam  is  still  issuing,  there  is  only  the  vapor  of 
water  in  the  cavity.  As  this  condenses  from 
cooling,  the  pressure  on  the  water  diminishes, 
and  it  boils  more  easily  from  the  heat  it  still 
contains ;  the  affusion  of  cold  water,  by  pro- 
ducing a  more  perfect  condensation,  occasions 
a  more  violent  ebullition.  The  hot  water, 
however,  increases  the  elasticity  of  the  uncon- 
dcnsed  vapor,  and  represses  the  boiling.  These 
alterations  can  be  produced  as  long  as  the 
water  in  the  vessel  is  warmer  than  the  cold 
water  poured  on  it.  When  cold,  the  space 
over  the  water  will  be  a  good  vacuum,  and 
if  we  turn  the  water  from  the  ball  into  the 
neck,  it  will  fall  like  lead,  with  a  smart  blow 
and  rattling  sound.  This  is  sometimes  called 
the  water-hammer.  The  perfection  of  the 
vacuum  can  be  tested  by  withdrawing  the  cork 
under  water  ;  the  pressure  of  the  atmosphere 
will  then  drive  in  a  quantity  of  water,  equal  to  the  vacuum 
produced  bv  the  first  expulsion  of  the  air. 

122.  Freezing  and   Boiling  in  a  vacuum. — A  little  ether 
under  an  air-jar  on  the  plate  of  the  air-pump  will  flash  into 
vapor  as  soon  as  the  pressure  is  removed   by  working  the 
pump ;   and  water   may  be  frozen 

by  its  own  evaporation,  over  a  good 
air-pump,  arranged  as  in  the  figure. 
The  water  is  contained  in  a  watch- 
glass  on  a  tripod,  over  a  shallow 
dish  of  sulphuric  acid,  and  the  whole  is  covered  by  a  low 
air-jar.  On  working  the  pump,  the  water  evaporates  so 
rapidly  in  the  vacuum  as  to  boil  even  at  72°,  its  vapor  is 
instantly  absorbed  by  the  sulphuric  acid,  and  in  this  way 
both  the  sensible  and  latent  heat  are  removed  so  rapidly,  that 
the  water  is  frozen  solid  while  still  apparently  boiling. 

123.  The     Cryophorus,   or   frost-bearer,  offers    another 


What  principles  are  here  brought  into  view  ?     How  is  the  absence 
of  the  air  made  evident  ?     122.  How  is  water  frozen  in  a  vacuum? 


88  HEAT. 

illustration  of  the  same  facts.     This  little  instrument,  invented 

by  Dr.  Wol- 
laston,  is  only 
a  bulb  of  glass, 
containing  a  lit- 
tle water,  and 

connected  by  a  long  bent  tube  with  another  bulb  or  protube- 
rance, which  is  empty  ;  the  space  over  the  water  is  a  vacuum, 
the  tube  having  been  sealed  when  the  water  was  boiling.  On 
placing  the  empty  stem  in  a  freezing  mixture  of  ice  and  salt, 
the  vapor  of  the  water  is  so  rapidly  condensed  as  to  freeze 
the  fluid  in  the  ball  which  is  remote  from  the  freezing  mixture. 

124.  Practical  application  of  these  facts  is  made  in  the 
arts  on  a  large  scale,  in  manufacturing  sugar.     The  boiling 
of  the  syrup  is  performed  in  vacuo,  in  large  pans  of  copper, 
holding  several   hundred    gallons,  the  air  and   vapor  being 
removed  from  the  vessels  by  a  steam-engine ;  the  syrup  is 
thus  rapidly  boiled   down  at  a  temperature  of  150°   to  180°, 
without   any  danger  of    burning.     Vegetable    extracts    nre 
frequently  made,  and    saline  solutions    boiled,  in    the  same 
way.     Nothing  in  the  arts  shows  more  clearly  the  value  and 
beauty  of  scientific  principles. 

125.  Elevation  of  the  Boiling  Point  by  Pressure. — If 
water  is  boiled  in  a  vessel,  which  can  be  closed  after  the 
escape  of  the  atmospheric  air,  as  in  the  brass  boiler  (a)  of 
the  annexed  figure,  we  can  easily  submit  it  to  any  desired 
degree  of  pressure,  and  thus  elevate  the  boiling  point.     This 
boiler    is    provided  with  a  thermometer   (c)  whose    ball    is 
within   the  steam  cavity  ;  and  also  with  a  barometer  tube, 
(A,)  which  descends  into  some  mercury,  placed  in  the  bot- 
tom.    It  is  supported  by  a  tripod  (f)  over  a  lamp,  (f,)  and  a 
sf op-cock  (d)  cuts  off  the  external  air.     As   soon    as  the 
water  in  it  boils,  the  steam  accumulates,  and,  pressing  on 
the  mercury,  forces  it  up  the  tube,  against  'the  imprisoned 
air.      The    relation   of   air   to   pressure    has    already    been 
explained,  (30.)     When  the  mercury  indicates  30  inches,  or 
double  the  pressure  of  the  air,  the  thermometer  will  indicate  a 
temperature  of  2500<5.  In  this  way  the  boiling  point  of  water  ha« 

123.  What  is  the  cryophorus  ?  Explain  the  principle  of  its  action. 
121.  What  practical  application  is  made  of  these  facts  ?  125.  How 
does  pressure  affect  the  boiling  point  ?  Explain  the  apparatus  here 
figured. 


VAPORIZATION.  89 

been  raised  to  429°-34,  or  nearly  to  the 
melting  point  of  tin;  the  pressure 
was  then  375  pounds  to  the  inch, 
or  25  atmospheres.  Mr.  Jacob 
Perkins  heated  steam  so  highly, 
that  a  jet  of  it  set  fire  to  combusti- 
ble bodies. 

126.  The  clastic  jwwer  of  steam 
:n    contact    with    water    is    limited 
only  by  the  strength  of  the  contain- 
ing  vessel:  if  steam  l>e  heated  with- 
out water,  (not  in  contact  with  i/,) 
then  its  elastic  or  expansive  power 
is  exactly  like  that  of  other  gases  or 
vaj>ors,  (88.) 

1 27.  The  increase  of  volume  in 
changing  from  a  liquid  to  a  gaseous 
state  is  such,  that  1  cubic  foot  of  water 
becomes  1700  cubic  feet  of  steam  ; 
or  a  cubic  inch  of  water   becomes 
nearly  a  cubic  foot  of  steam  ;  while 
1    cubic    foot  of  alcohol  and  ether 
yield,  respectively  493  and  212  cubic 
feet  of  vapor. 

Water  is,  therefore,  incomparably 
the  best  fluid  from  which  to  generate 
steam  for  a  moving  power  ;  for  its 
higher  boiling  point  is  more  than 
made  up  by  the  greater  volume 
of  its  vapor,  and  the  cost  of  • 
fuel  is  in  proportion  to  the  la- 
tent heat  of  equal  volumes  of  vapor.  Thus  water  is  superior 
to  ether  for  this  purpose,  in  the  proportion  of  2500  to  1000. 
The  latent  heat  of  steam  diminishes  as  the  heat  rises,  so 
that  the  heating  power  of  steam  at  400°  is  no  greater  than 
that  of  an  equal  volume  at  212°.  These  facts  sre  of  the 
greatest  value  in  the  arts. 


What  is  the  boiling  point  of  water  under  30  inches  of  mercury? 
How  high  has  it  been  raised  ?  126.  How  does  elevation  of  tem- 
perature affect  steam  ?  127.  What  is  the  increase  of  volume  from 
vaporization  of  water?  Of  alcohol  ?  Of  ether? 

8* 


90 


HEAT. 


/  128.    The    Steam-Engine. — The  principle  of  this  appa- 

itatus  is  simple,  and  easily  illustrated  by  the  simple  instrument 

a  here  figured,  which 

was    contrived     by 

Dr.  Wollaston.     A 

glass  tube  (a),  with  a 

bulb  to  hold  a  little 

water,  is  fitted  with 

a   piston.     A    hole 

passes     from     the 

under  side  through 

the     rod,    and     is 

closed  by  a  screw 

at  a.     This  screw 

is  loosened  to  ad- 
mit the  escape  of 
the  air,  and  the  water  is  boiled 
over  a  lamp  ;  as  soon  as  the  steam 
issues  freely  from  the  open  end 
of  the  rod,  the  screw  is  tighten- 
ed, and  the  pressure  of  the  steam 
then  raises  the  piston  to  the  top 
of  the  tube;  the  experimenter 
withdraws  it  from  the  lamp,  the 
steam  is  condensed,  and  the  air  pressing  freely  on  the  top  of 
the  piston  forces  it  down  again  ;  when  the  operation  may  be 
repeated  by  again  bringing  it  over  the  lamp. 

In  the  common  condensing  engine,  a  cylinder  (ci)  is  fitted 
with  a  solid  piston,  the  rod  of  which  moves  through  a  tight 
packing  in  the  cover,  and  to  it  the  machinery  is  attached.  A 
pipe  (d)  brings  the  steam  from  a  boiler  to  the  valve  arrange- 
ment, (c,)  by  which  the  steam  is  admitted,  alternately,  to 
the  top  and  bottom  of  the  cylinder  ;  and  also  an  alternate 
communication  is  opened  with  the  condenser,  (b.)  Thus, 
when  the  steam  enters  at  the  top,  (in  the  direction  of  the  ar- 
row,) that  at  the  bottom  of  the  piston  is  driven  through  the 
lower  opening  to  (b)  where  it  is  condensed.  The  valves  are 
:noved  at  the  proper  time  by  the  machinery. 

129.  Evaporation  from  the  surface  of  liquids  takes  place 


128.  Explain  the  principles  of  the  steam-engine  from  Dr.  Wollas- 
ron's  instrument.  Explain  the  general  structure  of  the  condensing 
engine  from  the  figure. 


VAPORIZATION. 


91 


at  all  temperatures,  while  ebullition,  it  will  be  remembered, 
occurs  only  at  a  particular  temperature  for  each  fluid.  Even 
snow  and  ice  waste  by  evaporation,  at  temperatures  too  low 
to  melt  them.  Mercury  rises  in  vapor,  even  at  the  temper- 
ature of  60°  ;  for  Dr.  Faraday  found  at  that  temperature  that  a 
slip  of  gold-leaf  suspended  in  a  close  vessel  was  whitened 
by  amalgamation  with  the  vapor  of  the  mercury. 
The  state  of  the  atmosphere  as  to  dryness  and 
pressure  influences  natural  evaporation,  which  is 
greatly  increased  by  heat  and  a  rapid  wind.  It 
must  be  remembered  that  all  the  water  which  falls 
to  the  earth  in  snow  and  rain  has  arisen  in  evapo- 
ration. That  natural  evaporation  takes  place 
only  from  the  surface  is  proved  by  its  being  en- 
tirely prevented  by  a  film  of  oil  on  the  surface  of 
the  fluid. 

180.  Influence  of  Pressure  on  Evaporation. — 
If  we  introduce  a  few  drops  of  water  into  the  va- 
cuum above  the  mercury  in  a  barometer  tube  (33), 
the  level  of  the  mercury  will  be  reduced  by  the 
vaporization  of  a  part  of  the  water.  The  tension 
of  the  vapor  is  increased,  by  a  rise  of  temperature  : 
we  may  slip  a  larger  tube  over  the  barometer 
tube,  the  lower  end  of  which  dips  under  the  mer- 
cury, and  then  fill  the  intervening  space  with  hot 
water.  The  vapor  of  the  confined  water  will 
force  down  the  column  of  mercury  in  direct  pro- 
portion to  the  temperature ;  and  by  means  of  a 
thermometer  and  a  scale  of  inches  we  can  tell 
exactly  the  tension  of  the  vapor  of  water  for  every 
temperature  under  212°. 

131.  Maximum  Density  of  Vapors. — If  we 
nearly  fill  with  mercury  three  barometer  tubes  closed  at  one 
end,  and  into  the  open  end  of  one  pour  a  little  ether,  into  the 
second  some  alcohol,  and  into  the  third  some  water,  and  then 
invert  them  with  their  mouths  beneath  mercury,  we  shall  see, 
on  withdrawing  the  finger  from  the  open  end,  that  the 


129.  What  is  the  difference  between  evaporation  and  ebullition  ? 
130.  How  does  pressure  affect  evaporation  ?  How  is  the  tension  of 
vapor  measured  ? 


92  HEAT. 

mercury  will  be  depressed  least  by  the 
water,  more  by  the  alcohol,  and  most  of 
all  by  the  ether,  (about  10  inches  at  60°.) 
The  addition  of  more  of  each  fluid  will  have 
no  effect  in  lowering  the  mercury,  the  tem- 
perature remaining  the  same.  There  is, 
therefore,  a  point  of  density  of  the  vapor 
which  cannot  be  passed  without  again  con- 
verting it  to  a  liquid.  This  is  easily  shown 
by  inclining  the  tube  containing  the  ether 
out  of  a  vertical  position ;  the  more  nearly 
horizontal  it  becomes,  the  less  ether  can  re- 
main in  vapor,  because  the  increased  pressure 
forces  it  into  a  fluid  state.  The  same  fact  is 
beautifully  shown  in  the  annexed  figure,  where 
the  barometer-tube  with  ether  is  depressed  in  a 
deep  cistern  of  mercury.  The  film  of  liquid 
ether  on  the  surface  of  the  mercury  in  the 
tube  is  seen  to  increase  as  the  tube  descends, 
until  the  ethereal  va|>or  is  all  reconverted  to  a 
fluid  ;  on  diminishing  the  pressure  of  the 
finger,  the  liquid  ether  again  flashes  into  vapor. 
The  weight  of  100  cubic  inches  of  aqueous 
vapor  at  212°  in  the  greatest  state  of  density 
ever  obtained,  is  14-90:2  grains;  while  the 
same  at  32°  is  only  '13(3  grains.  The  point 
of  maximum  density  of  a  vapor  is  lowered  by 
cold  as  well  as  by  pressure,  and  when  these 
two  effects  are  united,  we  can  convert  many 
gases,  which  arc  quite  permanent  at  the  com- 
mon pressure  and  temperature  of  the  air,  into  liquids,  and 
even  to  solids. 

132.  Diffusion  of  Gases  and  Vapors. — The  vapor  of 
water  will  rise  and  fill  a  confined  vessel  of  air,  and  have  the 
same  tension  as  if  no  air  were  present.  It  will  take  a  longer 
time  to  do  it,  but  as  much  will  ultimately  rise  as  if  the  space 
were  a  vacuum.  The  air  seems  to  be  an  impediment  only 
to  the  rapid  rise  of  the  vapor.  On  the  same  principle,  prob- 
ably, is  explained  the  curious  and  important  fact,  that,  when 
different  gases  are  in  contact,  they  will  not  remain  separate, 


131.  What  is  the  maximum   density  of  vapors  ?     Illustrate  this 
from  the  figure. 


VAPORIZATION.  93 

but  will  soon  mingle  uniformly,  even  against  the  force  of 
gravity.  Our  atmosphere,  for  instance,  is  composed  of  two 
gases,  the  specific  gravities  of  which  are  as  976  to  1130, 
and  we  might  suppose  that  the  heavier  would  be  at  ^ 
the  bottom,  as  would  be  the  case  in  two  such  liquids 
as  water  and  oil.  But  they  are  found  to  be  in  a  state 
of  uniform  mixture.  If  we  connect  together  by  a  tube 
two  bottles  containing,  one  a  light  gas,  hydrogen,  and 
the  other  a  heavier  gas,  oxygen,  and  place  the  light 
one  uppermost,  in  a  few  hours  we  shall  find  them  per- 
fectly commingled  ;  as  may  be  proved  by  the  fact,  that 
the  mixture  will  explode  violently  on  touching  a  match 
to  the  open  mouth  of  one  of  the  vessels,  which  we 
know  a  mixture  of  these  two  gases  will  always  do. 
The  same  efTect  will  take  place  through  a  very  fine 
tube,  or  even  through  a  plug  of  plaster-of-paris,  or 
through  a  membrane,  as  of  gold-beater's  skin.  The 
degree  of  condensation  of  the  air  or  vapor  has  no  effect 
in  the  operation  of  the  law  of  the  uniform  diffusion  of  gases. 
133.  Dew-Point. — Watery  vapor  is  never  absent  from  the 
"""tir;  but  its  quantity  is  very  variable,  depending  on  the  causes 
1  Already  named,  (129.)  When  the  air  is  highly  charged  with 
humidity,  it  deposits  dew  on  any  substance  colder  than  itself. 
A  glass  of  iced  water  in  summer  is  immediately  covered  with 
a  coat  of  condensed  vapor  from  the  surrounding  air.  When 
a  warm  humid  morning  succeeds  a  cool  night,  we  see  the 
pavements  and  walls  of  the  houses  recking  with  deposited 
water,  as  if  they  had  been  drenched  with  rain.  If  we  drop 
bits  of  ice  into  a  tumbler  of  water  having  the  same  temper- 
ature with  the  air,  and  watch  the  fall  of  a  thermometer 
placed  in  it,  we  can  note  with  accuracy  the  temperature  of 
the  water,  when  it  has  cooled  so  far  that  dew  begins  to  be 
deposited  on  the  clean  surface  of  the  glass.  This  tempera- 
ture is  called  the  dew-point ;  and  the  number  of  degrees  be- 
tween the  temperature  of  the  air,  and  of  water  cooled  to  that 
degree  at  which  dew  begins  or  ceases  to  be  deposited,  is  an  accu- 
rate indication  of  the  actual  dryness  of  the  air.  The  nearer  the 
dew-point  is  to  the  temperature  of  the  air,  the  more  moisture 
does  it  contain,  and  vice-versa.  In  this  climate,  in  summer, 
this  difference  amounts  often  to  40°  or  more,  and  in  India  it 

132.  Mention  the  facts  relating  to  the  diffusion  of  vapors  and 
gases.  Illustrate  this.  133.  What  is  the  dew-point  ?  How  does 
it  indicate  the  dryness  or  humrdity  of  the  climate  ? 


94 


HEAT. 


has  been  known  to  be  as  much  as  61°  ;  that  is,  with  an  ex- 
ternal temperature  of  90°,  the  dew-point  has  been  seen  as  low 
as  29°.  The  amount  of  moisture  in  the  air  has  a  great 
influence  on  the  indications  of  the  barometer,  and  it  is  always 
requisite,  in  making  barometrical  observations,  to  make  a 
correction  for  the  tension  of  the  vapor  of  water  in  the  air. 

134.  Hygrometers*  arc  instruments  to  determine  the 
amount  of  moisture  in  the  air.  One  much  used  is  called 
the  wet  bulb  hygrometer,  and  consists  of  two  sim- 
ilar delicate  mercurial  thermometers,  the  bulb 
of  one  of  which  is  covered  with  muslin,  and  is 
kept  constantly  wet  by  wa-  a 

ter,  led  on  to  it  by  a  string 
from  a  tube  in  the  centre. 
The  evaporation  of  the  water 
from  the  wet  bulb  reduces  the 
temperature  of  that  thermome- 
ter to  which  it  is  attached,  in 
proportion  to  the  dry  ness  of 
the  air,  and  consequent  rapidi- 
ty of  evaporation.  The  other 
thermometer  indicates  the  ac- 
tual temperature,  and  the  dif- 
ference being  noted,  a  mathematical  formula  en- 
ables us  to  determine  the  dew-point. 

But  the  most  delicate  and  beautiful  instrument 
for  this  use  is  that  of  Mr.  Daniell,  which  is  constructed  on 
the  principle  of  the  cryophorus,  (123.)  It  is  represented 
in  the  annexed  figure,  (a.)  The  long  limb  ends  in  a  bulb 
which  is  made  of  black  glass,  that  the  condensed  vapor 
may  be  more  easily  seen  on  it.  It  contains  a  portion 
of  ether,  into  which  dips  the  ball  of  a  small  and  delicate 
thermometer  contained  in  the  cavity  of  the  tube.  The  whole 
instrument  contains  only  the  vapor  of  ether,  air  having  been 
removed.  The  short  limb  carries  an  empty  bulb,  which  is 
covered  with  muslin.  On  the  support  is  another  thermome- 
ter, by  which  we  can  observe  the  temperature  of  the  air. 
When  an  observation  is  to  be  made  by  this  instrument,  a 
little  ether  is  poured  on  the  muslin :  this  evaporates  rapidly, 


134.  What  are  Hygrometers  ?     Describe  the  wet  bulb.     Describe 
the  Hygrometer  of  Prof.  Daniell. 


From  the  Greek  hitgros,  moist,  and  metron,  measure. 


VAPORIZATION.  95 

and  of  course  reduces  the  temperature  of  the  other  ball, 
(122.)  As  soon  as  this  has  fallen  to  the  dew-point,  the 
moisture  collects  and  is  easily  seen  on  the  black  glass.  At 
this  instant,  the  temperature  indicated  by  the  thermometers  is 
noted  down,  and  the  difference  gives  us  the  true  dew-point. 

135.  The  Spheroidal  state  of  bodies,  as  it  is  called,  is  a 
curious  and  instructive  instance  of  the  low  conducting  power 
of  vapors.     When  water  or  any  other  liquid  is  projected  in 
drops    on  a   surface,  heated  considerably  alx>vc   its  boiling 
point,  it  will  assume  a  spheroidal  form,  roll  about  with  activity, 
and  evaporate  with  extreme  slowness.     Water  assumes  this 
condition  at  298°  ;  and  a  grain  and  a  half  of  water  in  this 
state  at  392°  requires  3-30  minutes  to  evaporate  :  at  a  dull 
red  heat,  the  same  quantity  will  last  1*13  minutes,  and  at  a 
bright  red,  0-50,  the  rate  of  evaporation  increasing  with  the 
temperature.     The  water,  in    these   experiments,  docs   not 
touch  or  wet  the  hot  surface,  but  is   kept  at  a  sensible  dis- 
tance from  it  by  the  elastic  force  of  an  atmosphere  of  its  own 
vapor.     This  vapor    is  a  non-conductor,  and   its   formation 
abstracts  the  sensible  heat  from  the  fluid ;  so  that,  notwith- 
standing the  proximity  of  the  red-hot  metal,  the  temperature 
of  the  fluid  is  found  to  be  always  lower  than  its  boiling  point, 
being,  for  water,  206°,  for  alcohol,  168°,  and  for  ether,  91°. 
A   modification   of  this  process  enables  us  to  perform    the 
surprising  experiment  of  freezing  water  in  a  white-hot  crucible, 
by  the  aid  of  liquid  sulphurous  acid  in  the  spheroidal  state. 

136.  Liquefaction   and    Solidification    of  Gases. — We 
have  said  that,  by  the  united  aid  of  cold  and  pressure,  many 
gases  have  been  made  fluid,  and  even  solid.     No  degree  of 
mere  pressure,  not  even  50  atmospheres,  (or  750  Ibs.  to  the 
square  inch,)  can  alone  produce  this  result.     By  combining 
the  two  agents,  Dr.  Faraday  has  succeeded  in  reducing  fifteen 
aeriform  bodies  to  the  liquid  or  solid  state.     The  simple  appa- 
ratus required  for  many  of  these  results,  is  only  a  small  tube 

of  glass,  bent  as  in  the 
figure,  at  an  obtuse  angle, 
in  which  are  placed  the 
materials  for  generating 
the  gas ;  for  instance, 

135.  What  is  meant  by  the  spheroidal  state  ?  How  does  it  illus- 
trate these  principles  ?  Explain  the  experiments  mentioned  in  this 
paragraph.  Is  the  temperature  of  the  fluid  in  this  state  as  high  as 
its  boiling  point  ?  136.  How  are  gases  made  fluid  or  solid  ? 


96  HEAT. 

powdered  bicarbonate  of  soda  and  water  in  one  end,  and  sul- 
phuric acid  in  the  other,  to  generate  carbonic  acid  gas ;  they 
are  separately  introduced,  and  the  tube  then  sealed  by  the 
blow-pipe.  On  reversing  the  position  of  the  tube,  the  acid 
can  be  made  to  run  down  on  the  carbonate  of  soda,  and 
the  carbonic  acid  gas  will  be  set  free,  but  cannot  escape 
from  the  tube.  The  empty  end  is  then  placed  in  a  freezing 
mixture,  and  the  gas  is  condensed  into  a  liquid  by  its  own 
pressure.  Some  hazard  attends  these  experiments,  and 
the  operator  should  be  protected  by  gloves  and  a  mask 
of  wire-gauze  ;  for  the  tubes  occasionally  burst  under  the 
enormous  pressure,  and  might  wound  him  severely.  Car- 
bonic acid  treated  in  this  way  becomes  a  clear  transparent 
crystalline  solid,  at  temperatures  below  — 71°,  at  which  point 
it  melts  into  a  perfect  limpid  fluid,  which  is  not  so  heavy  as 
the  solid.  M.  Cagniard  de  la  Tour  has  shown,  that  at  a 
certain  temperature  and  pressure,  a  liquid  becomes  a  clear 
transparent  vapor,  or  gas,  having  the  same  bulk  as  the  liquid. 
At  this  temperature,  or  one  a  little  greater,  no  additional 
pressure,  however  great,  would  convert  the  gas  into  a  liquid. 
Dr.  Faraday  thinks  that  this  state  comes  on  with  carbonic 
acid  at  about  90°,  and  with  a  pressure  above  50  atmospheres. 
137.  Liquefaction  and  Solidification  of  Carbonic  Acid. 
— M.  Thilorier  has  contrived  an  apparatus  for  condensing 
carbonic  acid  on  a  large  scale.  The  arrangement  is  shown 
in  the  accompanying  figure ;  g  is  the  generator  of  the  gas,  a 
strong  cast-iron  vessel,  hung  by  centres  on  a  frame,  (J ;)  in 
it  is  put  the  requisite  quantity  of  carbonate  of  soda  and  water, 
and  a  tube  (a)  of  copper,  holding  an  equivalent  amount  of 
strong  sulphuric  acid ;  the  cap  is  strongly  screwed  in,  and 
the  position  of  the  apparatus  inverted,  by  turning  it  over  in 
the  frame ;  the  acid  then  runs  out  among  the  carbonate  of 
soda,  and  an  enormous  pressure  is  generated  by  the  succes- 
sive portions  of  gas  evolved  ;  after  a  time,  when  no  more 
gas  is  produced,  the  generator  is  connected  by  a  metallic  tube 
with  the  receiver,  (r ;)  stop-cocks  of  peculiar  construction 
are  fixed  on  the  top  of  both  vessels,  and  being  opened,  the 
liquefied  gas  collects  in  r,  which  is  cooled  by  a  freezing  mix- 
ture for  the  purpose  of  condensing  it.  In  this  way,  several 
charges  of  the  condensed  carbonic  acid  gas  are  accumulated 


Explain  the  process.     What  has  M.  Cagniard  de  la  Tour  shown  ? 
137.  Describe  M.  Thilorier's  apparatus  for  condensing  carbonic  acid. 


ELECTRICITY. 


97 


in  r.  It  can  then  be  drawn  off 
by  a  jot  (j)  secured  to  the  top, 
which  enters  a  metallic  box,  (&,) 
having  perforated  wooden  han- 
dles. The  rapid  evaporation  of 
the  condensed  gas  here  absorbs 
so  much  heat  from  the  rest,  that 
a  considerable  portion  is  convert- 
ed to  a  fine  white  solid,  like  dry 
snow.  The  author  has  repeat- 
edly formed  balls  of  this  snow  of 
considerable  size.  When  thus 
made  solid,  it  wastes  away  very 
slowly,  and  may  be  handled, 
and  moulded  with  ease.  If  suffered  to  rest  on  the  hand, 
however,  it  destroys  the  vitality  of  the  flesh,  like  a  hot  iron. 
It  is  now  in  a  condition  analogous  to  bodies  in  the  spheroidal 
state,  (133;)  being  surrounded  by  an  atmosphere  of  its  own 
vapor,  the  radiation  of  heat  to  it  from  surrounding  bodies  is 
cut  off,  and  it  acquires  the  very  low  temperature  of  — 148°. 
If  it  is  wet  with  ether  in  a  capsule  containing  mercury,  the 
latter  is  frozen  solid,  and  can  then  be  hammered  with  a  wooden 
mallet,  and  drawn  out  like  lead.  If  it  is  moistened  with  ether 
in  vacuo,  with  certain  precautions,  the  greatest  degree  of 
cold  yet  observed  is  produced;  viz:  174°  below  zero  of 
Fahrenheit.  The  greatest  cold  before  known  was  — 148°, 
and  the  greatest  natural  cold  ever  recorded  by  man  was 
— 60°,  which  was  found  by  Captain  Ross  in  his  polar 
voyages. 

We  now  see  how  entirely  the  gaseous,  liquid,  and  solid 
states  of  bodies  are  dependent  on  heat  and  pressure.  It 
is  more  than  probable  that  all  the  bodies  now  known  to  us 
as  permanent  gases  may  be  reduced  to  the  fluid  or  solid 
state,  by  means  similar  to  those  which  have  already  been 
used. 

IV.  ELECTRICITY. 

^-V^^  y 

138.  Tnere  is  a  remarkable  power  inherent  in  all  things, 
which  yte  call  electricity,*  and  which,  so  far  as  we  know, 

What  temperature  has  been  reached  by  aid  of  this  condensed 
gas  ?  How  is  the  lowest  artificial  temperature  found  ?  What  do 
we  now  see  from  these  facts  ? 


*  From  the  Greek,  electron,  amber,  the  substance   in  which  this 
9 


98  ELECTRICITY. 

is  inseparable  from  matter.  It  has  been  classed  with  light 
and  heat,  as  an  imponderable  agent,  and  is  doubtless  very 
closely  related  to,  if  not  identical  with  these  forces,  the  three 
being,  perhaps,  only  modifications  of  one  and  the  same 
power.  It  is  so  intimately  connected  with  matter,  as  to  be 
evolved,  in  some  form  or  degree,  with  every  change,  either 
mechanical  or  chemical,  which  matter  undergoes.  As  was 
said  of  heat,  (69,)  we  know  it  only  by  its  effects,  as  manifested 
on  or  through  matter.  We  shall  consider  this  power  under 
its  most  remarkable  forms  of  existence  or  manifestation, 
regarding  them  all,  however,  as  modifications  of  one  and  the 
same  thing.  These  are  (1,)  the  Electricity  of  Magnetism  ; 
(2,)  that  of  Friction,  or  Statical  Electricity  ;  (3,)  that  of 
Chemical  Action,  Galvanism,  or  Voltaism,  called  also, 
Dynamical  Electricity  ;  and  (4,)  Thermo-electricity,  or 
Electricity  from  Heat. 

1.  Magnetic  Electricity,  or  Magnetism. 

139.  Lode-stone.* — A  kind  of  iron-ore  has  been  known 
from  remote  antiquity  which  has  the  property  of  at- 
tracting to  itself  small  particles  of  iron,  and  which  is  called 
the  lode-stone.  By  contact,  it  can  impart  its  virtues  to  iron 
and  steel,  and  also  in  a  slight  degree  to  cobalt  and  nickel. 
As  it  abounded  in  Magnesia,  (a  province  of  ancient  Lydia,) 
it  was  called  by  Pliny,  magnes,  and  hence  the  name  magnet. 
A  bar  or  needle  of  steel,  which  has  received  the  magnetic 
^  influence,  when  suspended  on  a  point,  as  in  the 

figure,  will  be  found  to  have  a  directive  tend- 
ency, by  which  one  end  turns  invariably  to  the 
north.  The  terms,  -j-  and  — ,  (plus  and  minus,) 
are  also  used  to  indicate  the  north  and  south 
poles.  The  needle  is,  therefore,  said  to 
have  polarity,  and  the  end  turning  north  is 
commonly  called  the  north  pole,  and  the  other  end  the  south 

138.  What   is   said   of    electricity  ?     How  is  it  classed  ?     How 
divided,  (1  ?)  (2?)  (3  ?)  (4  ?)     139.  What  is  the  lode-stone  ? 

power  was  first  noticed  by  the  ancients,  more  than  600  years  B.  O 
Modern  philosophers  have  given  the  name  of  the  substance  to  the 
unknown  power. 

*  Sometimes  spelt  improperly  load-stone.     It  is  from  the  Saxon, 
laden,  to  lead  or  direct. 


MAGNETIC   ELECTRICITY.  99 

pole.  If  we  bring  the  north  end  of  a  magnetic  bar  near 
to  the  similar  end  of  the  suspended  needle,  ^ — j^.  -^ 
the  latter  will  move  away,  as  indicated  by  the  •'«•»«• 

arrows,  being  repelled  by  the  similar  power  of  the  bar.  If, 
however,  we  bring  the  end  N,  towards  the  opposite  end  of 
the  needle  S,  it  will  be  attracted  to  the  bar,  and  strive  to 
move  as  near  to  it  as  possible.  The  reverse  is,  of  course, 
true  of  the  opposite  end  of  the  bar.  If,  in  place  of  a  mag- 
netic bar,  we  had  used  a  bar  of  unmagnetic  iron,  we  should 
have  found  both  ends  of  the  suspended  needle  equally,  but 
less  powerfully,  attracted  by  it.  We  thus  learn,  (1,)  that  the 
magnet  has  polarity,  and  (*<J)  that  poles  of  the  same  name  re- 
pel, and  those  of  opposite  names  attract  each  other.  This 
is  the  simple  and  important  law  of  magnetic  action. 

140.  Induction  of  Magnetism. — The 
manner  in  which  a  magnet,  or  lode-stone, 
imparts  its  own  power  to  surrounding 
substances,  is  called  induction,  and 
i those  bodies  capable  of  manifesting  this 
power  are  said  to  be  magnetized 
by  the  inductive  influence.  Thus, 
a  series  of  bars  of  iron  laid  about 
a  magnetic  bar,  as  in  the  figure, 
will  all  become  magnetic  by  in- 
duction, while  they  are  under  the  influence  of  the 
magnet;  and  in  obedience  to  the  law  just  stated  above, 
their  ends  next  the  N  are  all  S,  and  their  remote  ends/ 
all  N.  Every  magnet  is  surrounded  by  an  atmosphere 
of  influence,  which  has  its  centre  in  the  poles  of  the 
magnet,  and  diminishes  as  the  square  of  the  dis- 
tance, being  in  this  respect  like  the  law  of  gravi- 
tation. This  decrease  of  force  is  prettily  illustrated 
by  an  experiment  shown  in  the  annexed  cut.  The  bar 
magnet  holds  a  large  key;  this  can  hold  a  second 
smaller  than  itself;  this,  a  nail ;  the  nail,  a  tack-nail  ; 
and  lastly,  a  few  iron-filings  are  held  by  the  tack-nail, 
and  the  whole  receive  their  magnetism  by  induction 
from  the  bar,  and  each  article  has  its  own  separate 
polarity :  an  n  and  *  (or  +  and  — )  pole  being  opposed  to 

Explain  its  action.  Can  its  virtues  be  imparted,  and  to  what  ? 
What  do  we  know  of  the  suspended  needle,  (1  ?)  (2  ?)  140.  What 
is  induction  of  magnetism  ?  Illustrate  this  ?  How  is  the  power 
as  regards  distance  ?  Give  an  experimental  illustration. 


100  ELECTUILITV. 

each    other  at   every  junction.     This  effect  will  take  place 
through  a  glass-plate,  or  a  small  interval  of  air. 

141.  Permanent  Magnets. — These  can  be  made  only  of 
hardened  steel.  Soft  iron  and  steel  are  magnets  only  while 
under  the  power  or  influence  of  other  magnets,  and  lose 
their  own  power  as  soon  as  removed  from  them.  Mag- 
netism is  imparted  by  '  touch?  as  it  is  technically  called,  from 
a  previously  existing  magnet.  An  umnagnetic  bar  of  hardened 
steel,  when  properly  rubbed  by  the  poles  of  a  magnet,  will 
itself  soon  acquire  polarity  and  magnetic  power.  Every 
magnet  is  considered  as  made  up  of  a  great  number  of 
small  magnets,  so  to  speak,  each  particle  of  steel  having 
polarity,  and  attracting  and  repelling  every  other.  We 
cannot  conceive  of  one  sort  of  polarity  existing  without  the 

Hunan*   n  s  n  s  n  .v  n  s  n  s      other.     Thus,  ill  the  figure, 

N£jg;j  :'3'j5  ^S-.SL.Ss  we  see  a  magnified  reprc- 

c^o5a5c=5cJ5c3cd5cj5  sentation  of  this  condition. 
Each  little  magnet  has  its  own  n  and  s.  Those  which  occupy 
the  middle  of  the  bar,  being  acted  on  alike  in  all  directions, 
can  show  no  power  ;  but  the  force  accumulates  toward  each 
end,  until  we  find  the  greatest  power  in  the  last  range  of 
particles,  which  we  term  the  poles. 

If  we  dip  a  magnetic  l>ar  in  iron- filings,  we  shall  find  only 
the  ends  attracting  a  tuft  of  the  metallic  particles,  while  the 
middle  is  free.  If  two  magnetic  bars,  however,  like  the 
figure,  are  placed  together,  (  +  and  — ,)  and  a  sheet  of 
paper  laid  over  them,  they  will  attract  iron  filings  scattered 

on  the  paper,  in  the  way 
represented  in  the  figure  ; 
here  a  pair  of  central  poles 
have  power  to  attract  the 
iron,  which  the  middle 
part  of  the  simple  bar  had  not.  The  particles  of  iron 
arrange  themselves  in  what  arc  called  magnetic  curves.  If 
the  paper  is  jarred,  this  effect  is  rendered  more  striking. 

14*2.    Artificial   Magnets   are    made   of   all    forms,    tin- 
most    common    being    the    so    called    horse-shoe    magnet, 
U    shaped   like  the  annexed  figure.     It  is  found  that  the 
power    of    magnets    is    much    increased     by    uniting 


111.  How  arc  permanent  magnets  made  ?  How  is  the  power  sup- 
posed to  be  distributed  ?  Why  have  the  polos  more  power  than  the 
centre?  If  two  bars  are  laid  together,  how  is  it?  142.  What 
Ibrms  are  given  to  artificial  magnets  ? 


MAGNETIC    ELECTRICITY.  101 

several  thin  plates  of  hardened  steel,  each  of  which  is  sepa- 
rately magnetized.  A  bar  of  soft  iron,  called  the  keeper,  is 
placed  across  the  poles  of  a  u  magnet,  to  prevent  it  from 
losing  power;  and  if  it  be  made  to  hold  a  weight  nearly 
equal  to  its  power,  it  will  be  found  to  gain  strength  daily,  and 
in  like  manner  to  lose  its  magnetism  if  unemployed. 
><ll43.  The  Earth's  Magnetism. — The  earth  is  a  gprfat^ 
.Tiiagnet,  and  the  magnetism  which  we  see  in  bars  of  steel 
ana  the  lode-stone,  is  the  result  of  induction  (139)  from  the 
earth.  The  magnetic  poles  of  the  earth  are  not  in  the  same 
points  with  the  poles  of  revolution  or  the  axis  of  the  earth,  and 
for  this  reason  the  magnetic  needle  does  not  point  to  the  true 
north  and  south,  but  varies  from  it  more  or  less,  and  differs 
at  different  times,  as  the  magnetic  pole  alters  its  position. 
This  is  called  the  variation  of  the  needle,  and  amounts,  at 
New  Haven,  to  6°  10'  W.,  (in  1840,)  and  at  Philadelphia 
to  3°  52'  W.,  (in  1837.)  As  unlike  poles  attract  each  other, 
the  end  of  the  needle  pointing  north  is,  in  fact,  its  south  pole, 
viewing  the  earth  as  a  magnet. 

The  magnetism  of  the  earth  is  beauti- 
fully shown  by  the  dipfring  needle,  repre- 
sented in  the  annexed   figure.     The  needle 
(/*)  is  s»s|>ended  on  the  horizontal  bar,  («,) 
so  as  to  move  in  a  vertical  plane,  instead 
of  horizontally,  as  in  the  compass-needle. 
The  graduated  vertical  circle  (r)  is  placed  in 
the  magnetic  meridian,  and  the  needle  then 
assumes,  in  this  latitude,*  the  position  shown  in  the  figure, 
dipping  down  at  an  angle  of  73°  26'-7.     Over  the  magnetic 
equator  it  would  stand  horizontal,  being  equally  attracted  in 
both  directions.     At  either  magnetic  pole  it  would    be  ver- 
tical. 

The  horizontal  variation  of  the  needle,  its  dip,  and  the 
intensity  of  the  polar  attraction,  are  subject  to  daily  and  local 
changes,  from  the  fluctuation  in  the  amount  or  direction  of 
this  force ;  and  daily  and  even  hourly  observations  have  now 

143.  What  is  said  of  the  earth's  magnetism  ?  How  is  it  shown  ? 
Is  the  magnetic  pole  coincident  with  the  pole  of  revolution  ?  What 
is  dip,  and  what  variation  ?  Are  they  constant  ? 


*  Lat.  41°  IS',  Ion.  17°  58',  in  September,  1839. 
9* 


10*2  ELECTRICITY. 

for  several  years  been  made  in  all  parts  of  the  world,  to 
determine  with  accuracy  the  limit  of  these  variations,  and  the 
laws  which  govern  them. 

144.  Magnetism  from  the  earth  is  induced    in  ail    bars  of 
steel  or  iron,  which  stand  long  in  a  vertical  position.     Tongs 
and  blacksmiths'  tools  are  often  found   to  be  magnetized.     A 
bar  of  iron  held  in  the  magnetic   meridian,  and  at  the  proper 
dip,  becomes  immediately  magnetic  from  the  induction  of  the 
earth;  and  the  effect   may  be   hastened  by  striking  it  on  the 
t'iul  with  a  hammer;  the  vibration  seems  to  aid  in   inducing 
the  magnetic  force.     The  tools  used   in   boring  and  cutting 
iron  are  generally  found  to  be  magnets. 

145.  Magnetics  and Diamagnetics, — Dr.  Faraday, in  1845, 
made  the  important  discovery  that  all  solid  and   fluid  sub- 
stances were  subject  to  the  influence  of  a  powerful   magnet, 
but  in  a  manner  different  from  tint  in  which  iron  and  nickel 
are  influenced  by  the  magnetic  force.     We  shall  presently  see 
(166)  that  a   bar  of  iron  suspended  on  a  pivot  will   take  a 
place  at  right  angles  to   the  direction  of  the  magnetic  or  gal- 
vanic current,  or  will  come  to  rest  in  the  equator  of  magnetic 
force.     Now  a   bar  of  bismuth,  or  a   stick   of  phosphorus, 
under  the  same  circumstances,  will  act  in  a  manner  precisely 
the  reverse  of  the  iron,  and  will  come  to  rest  in  the  magnetic 
or  polar  plain1.     All  bodies,  which  under  the  magnetic  power 
net   like  iron,  are  called   magnetics,  while   those  which  re- 
semble bismuth   in  their  behavior -under  the  same  circum- 
stances, arc  called  diamaguctics.    A  few  bodies  of  each  class 
are  enumerated  in  the   following   list,  where  we  observe  that 
iron  and   bismuth  are  at  the  extremes,  each   standing  as  the 
type  of  its  own  class,  while  air  and  vacuum  occupy  the  zero, 
or  neutral  point  of  quiescent   inactivity.     Iron,  nickel,  cobalt, 
manganese,  palladium,  crown-glass,  platinum,  osmium, — 0° 
air   and   vacuum,   arsenic,  ether,  alcohol,  gold,  water,  mer- 
cury,   flint-glass,    tin,    heavy-glass,    antimony,    phosphorus, 
bismuth.     It  is  a  curious  sight  to  see  a  piece  of  wood,  or  of 


lit.  How  are  bars  of  iron  and  steel  affected  by  the  earth's  mag- 
netism ?  115.  What  was  Faraday's  discovery  in  1815  ?  Into  what 
two  classes  are  bodies  divided  in  reference  to  their  behavior  under 
magnetic  influence?  Of  which  is  iron  the  type  ?  Of  which  is  bis- 
muth ?  How  are  the  classes  contrasted  ?  Enumerate  a  few  of 
each  class.  Is  this  action  confined  to  metals  ?  Mention  snm<» 
singular  examples. 


KLKCTRrCITY    OF    FRICTION. 


103 


beef,  or  an  apple,  or  n  bottle  of  water,  repelled  by  a  magnet ; 
or  taking  ihe  leaf  of  a  live  and  hanging  it  up  between  the 
poles,  to  observe  it  lake  an  equatorial  position. 

2.  Electricity  of  Friction ;  or  Statical  Electricity. 

140.  Electricity  is  rro/rrrf  by  several  of  the  same  causes 
which  we  have  already  (60)  named  as  sources  of  heat. 
Friction  excites  it  abundantly ;  chemical  action  still  more 
It  attends  animal  life,  and  is  powerfully  exhibited  in  som.1 
animals,  as  in  the  torpedo,  and  electrical  eel :  heat  evolves  it, 
and  wo  have  reason  to  believe  that  the  sun's  rays  are  jx^r- 
petually  exciting  electrical  currents  in  the  earth.  Like  heat, 
it  neither  adds  to  or  subtracts  from  the  weight  of  matter : 
but  unlike  heat,  it  produces  no  change  in  dimensions,  and 
does  not  atlivt  the  power  of  coltesion  in  bodies.  In  |towerful 
discharges,  however,  it  overcomes  cohesion  by  rending  or 
fusion.  All  matter  is  subject  to  its  influence,  and  it  can  be 
transferred  from  an  excited  body  to  one  previously  in  a  neu- 
tral stale. 

147.  Electrical  Excitement. — If  we  briskly 
rub  a  glass  tube  with   warm  and   dry  silk,  and 
bring  it  near  to  any  light  substance,  as  a  leather 
susjxnuled   by  a  thread,  a  flock   of  cotton,  some 
shreds  of  silk,  or,  as  in  the  figure,  to  two  balls 
of  pith,  suspended  on  a  hook   by  delicate  wire, 
the   light   substances  will  at  first  be  strongly  attracted  to  the 
tube,   but  in  an   instant  will  fly  oil" 
again,  as  if  repelled  by  some  unseen 
force,  and  any  further  effort  to  attract 
them   to  the  excited  glass  will  only 
cause  their   further  removal.     Ivach 
separate   thread   of    silk   and    each 
pith-hall   seems  to   retreat  as  far  as 
possible  from  the  jjlass  tube  and  from 
: ho  other  threads.     An  artificial  head 
of  hair  or  shreds  of  dry  paper  shows 
this    in    a   striking    manner,    when 
placed  on  the  conductor  of  an  excited 
electrical  machine.    Each  hair  stands 


14i>.  How    is    electricity     evolved  f       Contrast 
147.  Explain  The  first  facts  in  electrical  excitement 
pith-ball*  and  head  of  hair  affected  t 


it    with    heat. 
How  are  the 


104. 


ELECTRICITY. 


aloof  from  every  other,  as  if  instinct  with  hatred.  If  now, 
in  the  place  of  the  glass  tube,  we  use  a  stick  of  sealing-wax, 
rubbed  with  dry  flannel,  and  present  this  to  the  pith-ball 
which  has  been  excited  by  the  glass  tube,  we  shall  find  a 
very  strong  attraction  manifested  between  them  ;  the  light 
substance  previously  excited  by  the  glass,  will  move  to  the  ex- 
cited resin  much  more  actively  than  a  substance  not  previously 
excited  in  this  way  ;  and  two  substances  separately  excited, 
one  by  the  glass  and  the  other  by  the  resin,  will  attract  each 
other  with  equal  power.  One  of  these  is  called  vitreous,  and 
the  other  resinous  electricity.  These  simple  phenomena  form 
the  basis  of  all  electrical  science. 

^J      148.  Electrical  Polarity. — We  see  in  the  facts  just  stated 
/a  strong  resemblance   between  the  two  sorts  of  electrical  ex- 
/    citement  and  the  opposite  powers  of  the  magnet.     The  vitreous 
is  to  the  resinous  electricity  as  the  north  pole  of  a  magnet  is 
to  the  south.     Hence  we  call   the  vitreous  the  positive  elec- 
tricity, and  the  resinous  the  negative  electricity.     Each  par- 
ticle   of    matter    thus 
influenced  by  electrical 
excitement   must  have 
polarity,  like  the  mag- 
netic needle,  attracting 
and  repelling,  accord- 
ing as  it  is  acted   on  by  like  or  unlike   forces.     Thus  a  row 
of  pith-balls,  as  in  the   figure,  will   all    become   excited   b 
induction,  or  influence,  and   the   signs   plus   and   minus  wi 
explain  how  they  stand  related   to  each   other.     Magnetism, 
as  it  is  usually  understood,  is  confined  to  two  or  three  metals  ; 
while  electricity  can,  with   proper   precautions,  be  excited  in 
all  substances. 

We  cannot  conceive  of  one  sort  of  electrical  excitement 
existing  without  the  other ;  thus  the  glass  tube  is  -f ,  but  the 
silk  which  rubs  it  is  — ,  and  vice  versa,  the  resin  is  — ,  but 
the  flannel  is  -f . 

149.  Electrical  Equilibrium. — All  cases  of  electrical  ex- 
citement are  due  to  a  disturbance  of  the  electrical  equilibrium, 
or  balance  of  power,  which,  aside  from  disturbing  causes, 

If  wax  is  used  in  place  of  glass,  what  happens  ?  What  are  these 
two  electricities  called  ?  148.  What  analogy  do  we  see  between  the 
two  electricities  and  the  magnet  ?  What  names  do  we  give  to  them  ? 
Can  one  sort  of  electricity  exist  without  the  other  ?  149.  What  is 
electrical  equilibrium  ? 


ELECTRICITY  OF  FRICTION.  105 

naturally  exists  among  surrounding  bodies;  and  the  intensity 
of  the  electrical  action  is  directly  proportioned  to  the  amount 
of  that  disturbance.  The  more  unlike  in  electrical  state  a 
body  becomes  to  surrounding  substances,  the  more  energetic 
will  be  the  display  of  electrical  power.  The  opposite  states 
are,  however,  always  in  such  proportion  as  exactly  to  neu- 
tralize each  other  in  any  two  substances  which  have  been 
mutually  excited,  as  glass  and  the  silk  rubber. 

150.  Theories  of  Electricity. — Two  theories  have  been 
proposed  to  explain  the  ordinary  phenomena  of  electricity. 
The  first  is  that  proposed  by  our  distinguished  countryinnn, 
Dr.  Franklin,  (and  called  the  Franklinian  hypothesis,}  which 
is  very  simple  and  ingenious.  It  supposes  that  thorn  is  a 
simple,  subtle,  and  highly  elastic  fluid,  which  pervades  all 
matter.  This  fluid  is  self-repellent,  but  attracts  all  matter, 
or  its  ultimate  particles;  these  particles  of  matter  are  con- 
sidered as  also  self-repellent,  when  deprived  of  or  possessing 
more  than  their  natural  quantity  of  electricity,  and  as  natu- 
rally attracting  when  they  are  in  opposite  conditions.  In  the 
natural  state  of  bodies,  this  fluid  is  uniformly  distributed,  and 
its  increase  or  diminution  produces  electrical  excitement. 
Accordingly,  when  a  glass  tube  is  rubbed  with  a  silk  hand- 
kerchief, the  electrical  equilibrium  is  disturbed,  the  glass 
acquires  more  than  its  natural  quantity,  and  is  over-charged, 
the  silk  possesses  less,  and  is  under-charged. 

The  second  hypothesis  is  that  of  Du  Fay,  who  conjectured 
that  electrical  phenomena  were  due  to  two  highly  elastic, 
imponderable  fluids,  the  particles  of  which  are  self-repellent, 
but  attractive  of  each  other.  These  two  fluids  exist  in  all 
unexcited  bodies  in  a  state  of  combination  and  neutralization, 
when  no  electrical  phenomena  are  seen.  Friction  occasions 
the  separation  of  the  fluids,  and  the  electrical  excitement  in  a 
body  continues  until  an  equal  amount  of  opposite  electricity 
to  that  excited  has  been  restored  to  it. 

According  to  Dr.  Franklin's  theory,  the  two  states  are 
denominated  positive  and  negative ;  according  to  Du  Fay, 
they  arc  distinguished  as  vitreous  and  resinous.  We  can  use 
either  of  these  terms  indifferently,  however,  without  commit- 
ting ourselves  to  either  theory,  both  of  which  cannot  be  true. 
The  real  use  of  such  terms  is,  to  enable  us  to  obtain  clearer 

150.  Name  the  two  theories  of  electricity.  What  is  the  Frank- 
linian hypothesis  ?  What  is  Du  Fay's  view  ?  What  are  these  two 
theories  called  / 


106  ELECTRICITY. 

notions  of  the  relation  of  the  several  phenomena ;  and  the 
hypothesis  which  they  express  serves  as  a  thread  of  phi- 
losophy hy  which  we  connect  our  separate  facts. 

151.  Conductors  and  Insulators  of  Electricity. — The 
pith-balls  or  glass  tubes,  which  have  been  electric-ally 
excited,  return  to  a  natural  state  very  slowly  indeed,  if  left 
untouched,  in  dry  air.  But  the  hand,  or  a  metallic  rod,  will 
at  once  restore  them  to  the  unexcited  state,  while  dry  silk, 
glass,  and  resin,  will  not  remove  the  excitement.  Bodies  are, 
therefore,  divided  into  conductors  and  non-conductors  of  elec- 
tricity, or,  more  properly,  into  good  and  bad  conductors. 
The  electrical  discharge  takes  place  through  good  conductors, 
(as  the  metals,)  with  an  inconceivable  velocity,  which  can 
be  compared  only  to  the  velocity  of  light.  Among  good 
conductors,  in  the  order  of  their  conducting  power,  are  the 
metals,  charcoal,  plumbngo,  and  various  fused  chlorids, 
strong  acids,  water,  damp  air,  vegetable  and  animal  bodies ; 
among  imperfect  conductors  are  spermaceti,  glass,  sulphur, 
fixed  oils,  oil  of  turpentine,  resin,  ice,  diamond,  and  dry 
gases.  The  latter  substances  are  also  called  insulators, 
because  by  their  aid  we  can  insulate  or  confine  electricity. 

15*2.  Electroscopes,  or  Electrometers. — The  kind  of  elec- 
trical excitement  in  a  body  is  ascertained  by  a  very  simple 
apparatus,  called  an  electroscope.  The  pith-balls  (147) 
serve  this  purpose  very  well.  We  excite  them  by  electricity 
of  a  known  kind,  as  of  an  excited  glass  tube 
brought  into  actual  contact  with  them,  and  then 
we  bring  near  them  the  body  whose  electrical 
state  we  wish  to  learn :  if  they  are  still  further 
repelled,  we  conclude  that  the  body  in  question 
has  vitreous  or  positive  electricity;  but  if  they 
arc  attracted,  we  conclude  that  the  reverse  is  true. 
The  gold-leaf  electrometer  is,  however,  a  much 
more  sensitive  and  delicate  test  of  electrical  ex- 
citement, and  consists  of  two  leaves  of  gold, 
suspended  in  an  air-jar,  and  communicating  by  a  wire  with 
a  small  plate  of  brass ;  the  approach  to  this  plate  of  a  body 
in  any  degree  excited,  will  occasion  an  immediate  movement 
of  the  gold-leaves,  from  which  we  can  tell  the  nature  of  the 

What  is  the  use  of  such  theories?  151.  What  are  conductors  ? 
What  are  insulators  ?  Name  some  of  each.  152.  What  is  an  elec- 
troscope ?  How  do  we,  by  means  of  it,  ascertain  the  kind  of  elec- 
tricity ? 


ELECTRICITY   OF    FRICTION. 


107 


excitement,  as  above  described,   having  previously  imparted 
to  the  gold  leaves  a  particular  kind  of  electricity. 

153.  The  Electrical  Machine. — The  principle  of  the 
common  electrical  machine  will  be  easily  understood,  after 
what  has  been  said. 
Two  forms  of  this 
machine  are  in  com- 
mon use,  the  cylinder 
and  the  plate  machine : 
a  good  view  of  the 
latter  is  presented  in 
the  annexed  figure ;  d 
is  a  wheel  of  plate- 
glass,  turned  on  an 
axis  by  a  handle.  The 
electricity  is  excited 
by  the  friction  of  two 
cushions  or  rubbers, 
(e,  e,)  which  press 
against  the  plate,  and 
are  covered  with  a  soft 
amalgam  of  mercury, 
tin,  and  zinc,  which 
greatly  heightens  the 
effect.  The  rubbers  are  connected  with  the  earth  by  a 
metallic  chain,  (b.)  The  excited  glass  delivers  its  electricity 
to  several  sharp  points  of  wire  attached  to  the  bright  brass 
arms,  and  connected  with  the  great  conductor,  (a.)  The 
conductor  and  plate  are  perfectly  insulated  by  glass  supports. 
When  thus  arranged,  and  the  machine  is  turned,  bright 
sparks  of  a  violet  color,  forming  lines  like  lightning,  will  dart 
with  a  sharp  sound  to  any  conducting  substance  brought  near 
to  the  great  conductor.  This  is  positive  electricity.  If  nega- 
tive electricity  be  wanted,  we  must  insulate  the  rubbers,  and, 
connecting  the  conductor  with  the  earth,  draw  the  sparks 
from  the  rubber. 

Every  care  must  be  taken  in  the  use  of  an  electrical  appa- 
ratus, to  keep  it  clean  and  smooth,  and  particularly  free  from 
moisture.  Dust  acts  as  so  many  points  to  discharge  the 
fluid,  and  moisture  deposits  itself  in  a  thin  film  over  the  insu- 
lators, and  prevents  the  accumulation  of  power. 


153.  Explain  the  electrical  machine.     How  is  negative  electricity 
obtained  ?     What  care  is  to  be  used  in  keeping  an  electrical  machine  ? 


108 


ELECTRICITY. 


154.  The  Lcyden  Jar,  or  lria/,  is   the  simple  means  by 
which  the  experimenter  collects  and  transfers  a  portion  of 
the  electricity  evolved  by  his  machine,  and   applies  it  to  the 
purposes  of  experiment.     The  Loydcn-jar,   (so  called    from 
the  place  where  it  was  first  invented,*)  is  only  a  glass  bottle, 
covered  inside  and  out  with  tin-foil  up  to  the  line  seen   in  the 

figure.  A  brass  ball  communicates  by  a  wire 
and  chain  with  the  interior  coating,  the  mouth 
being  stopped  by  a  cover  of  dry  wood.  On 
approaching  the  ball  to  the  conductor  of  the 
electrical  machine,  when  in  action,  a  series  of 
vivid  sparks  will  l>e  received  by  it,  and  a  great 
accumulation  of  vitreous  electricity  takes  place 
in  the  interior,  provided  the  exterior  be  not 
insulated.  On  forming  a  connection  by  a  con- 
ductor between  the  interior  and  exterior  surfaces, 
the  equilibrium  is  at  once  restored  by  a  rush  of 
the  opposing  forces,  accompanied  with  a  brilliant  flash  of 
artificial  lightning,  and,  if  the  hand  of  the  operator  is  the 
conducting  medium,  a  violent  shock  is  felt,  commonly  known 
as  the  electrical  shock.  A  series  of  such  jars  arranged  so 
as  to  be  charged  by  one  machine,  is  called  an  electrical 
battery. 

155.  The  Eh'ctrojrfiorus^  is  a  convenient  mode  of  obtain- 

ing an  electrical  spark,  when  no 
electrical  machine  is  to  be  had, 
and  consists  of  a  shallow  tray  or 
dish  of  tin,  (or  a  wooden  box,) 
the  size  of  a  dining  plate,  partly 
filled  with  melted  shellac,  (a,)  or 
some  other  resinous  preparation, 
made  as  smooth  as  possible.  A 
disc  of  brass  (b)  with  a  glass  handle  is  provided,  and  the  bed 
of  resin  is  rubbed  with  a  dry  flannel  or  cat-skin;  this  excites 
negative  electricity,  and  the  metal  disc  is  then  laid  on  the 
excited  surface,  and  touched  with  the  finger.  A  coating  of 

154.  What  is  the  Leyden-jar,  and   how  used  ?     155.  What  is  an 
electrophorus,  and  how  made  and  used  ? 


*  This  instrument,  attributed  to  one  Cunaeus,  of  Leyden,  in  1746, 
has  done  as  much  for  statical  electricity  as  has  the  pile  of  Volta  for 
galvanism. 

f  From  the  Greek,  electron,  and  pkero,  I  carry. 


ELECTRICITY  OF  CHEMICAL  ACTION.  109 

positive  electricity  is  induced  on  it,  and  it  may  be  raised  by 
the  handle,  and  discharged  by  a  conductor,  giving  a  vivid 
spark,  sufficient  to  explode  gases.  The  resinous  electricity 
not  being  conducted  away  from  the  shellac,  the  spark  may 
be  repeated  as  long  as  the  excitement  lasts. 

156.  A  jet  of  high  steam  issuing  from  a  locomotive  or 
other  insulated  steam-boiler,  will,  with   certain  precautions, 
give  a  stream  of  electrical   sparks  more  powerful  than  any 
electrical   machine.     This  has  been  called  hydro-electricity, 
and  is  produced  by  the  friction  of  the  hot  steam  on  the  edges 
of  the  orifice  from  which  the  steam  issues. 

157.  Thunder  and  Lightning. — These  common  natural 
phenomena  arc  due  to  the   passage  of  electricity  from  one 
cloud   to  another,  or   from  a  cloud   to  the  earth,  which  is 
usually  attended  with  a   brilliant  flash  and   loud  explosion. 
Dr.  Franklin  first  suggested  and   proved  the  lightning  of  the 
atmosphere  to  1x3  the  same  thing  as  the  machine  electricity, 
and  contrived  an  electrical  kite  by  which  he  drew  the  lightning 
of  the  clouds  to  the  earth.*     In  a  thunder-storm   the  electri- 
cal   cloud,   the    intervening   air,   and    the   earth,    represent 
respectively  the  inner  and   outer  coatings  of  the  Leyden-jar ; 
the  air  being  the  non-conductor  through  which  the  discharge 
finally  takes  place.  / 


3.  Electricity  of  Chemical  Action^— Galvanism,  or  Voltaism. 

159.  We  have  found /the  electricity  of  friction,  or  ma- 
chine electricity,  to  be  endued  with  great  energy,  passing 
with  a  vivid  spark  through  a  considerable  thickness  of  dry 
air,  and  capable  of  being  insulated  by  non-conductors,  so  as 
to  be  easily  transferred  and  managed,  as  in  the  Leyden-jar. 
Moreover,  we  know  that  dryness  and  insulation  from  the 
earth  are  essential  to  its  excitation,  by  artificial  means. 
We  shall  now  see  how  strongly  in  these,  as  well  as  in  many 
other  respects,  it  is  contrasted  with  the  sort  of  electricity 

156.  What  is  said  of  the  electricity  of  high  steam  ?  157.  What 
are  thunder  and  lightning  ?  How  are  the  conditions  of  a  thunder-storm 
like  the  Leyden-jar '/  What  was  Franklin's  discovery  about  lightning  ? 
158.  What  leading  properties  have  we  observed  in  machine  electri- 
city? 


•  "  Eripuit  ccelis  fulmen  sceptrumque  tyrannis." 
10 


110  ELECTRICITY. 

which  is  the  product  of  chemical  action,  and  best  known  "as 
Galvanism,  or  Voltaism.* 

159.  Origin  and  Discovery  of  Galvanism. — Accident  led 
to  the  origin  of  the  science  oT  galvanism  in  1790.J  Gal- 
vanij  observed  that  the  freshly  prepared  legs  of  a  frog  were 
convulsed,  when  brought  within  the  influence 
of  a  powerful  electrical  machine  in  action. 
He  at  once  believed  that  he  had  discovered 
in  electricity  the  secret  spring  of  life  and 
nervous  power.  Volta,  however,  reasoned, 
that  the  convulsions  were  in  no  way  con- 
nected with  animal  life,  but  that  the  muscular 
contractions  were  excited  in  the  legs  of  the 
frog  by  induction  from  the  active  machine; 
this  effect  being  produced  through  the  influ- 
ence of  two  metals,  which,  at  the  time,  were 
in  contact  with  the  naked  flesh.  This  ex- 
periment is  easily  repeated  on  the  legs  of  a 
frog,  from  which  the  skin  has  been  recently 
stripped.  They  arc?  suspended  by  a  silver  or  platinum  wire, 
or  a  wire  of  any  metal,  passed  under  the  crural  nerves,  which 
are  easily  found,  by  gently  separating  the  large  muscles  of 
the  legs  at  a.  A  slip  of  zinc,  bent  so  as  to  touch  at  the  same 
time  the  toes  and  the  wire  of  suspension,  will  occasion  violent 
convulsions  in  the  legs.  This  irritability  is  lost  soon  after 
death. 


159.  When,   how,   and    by   whom,   was    galvanism   discovered  ? 
Explain  the  experiment  with  the  frog's  legs. 


*  This  sort  of  electrical  excitement  is,  also,  frequently  called  the 
"electricity  of  contact,"  because  actual  contact  of  the  metals  em- 
ployed was  supposed  to  be  required.  It  is  likewise  called  dynami- 
cal electricity,  (from  f/Hnami*,  power,)  and  "  current  affinity." 

f  Accident,  properly  considered,  never  discovered  any  philosophical 
principle.  The  minds  of  philosophers  had  been  ripening  for  fifty 
years  for  Volta's  discovery,  and  the  twitching  of  the  frog's  legs,  like 
Newton's  apple,  was  only  the  spark  which  fired  the  train  that  had 
been  long  laid. 

t  Prof.  Galvani  lived  at  Bologna,  in  Italy,  and  Volta  of  Pavia  waa 
his  nephew  and  pupil ;  although  Galvani  made  the  first  observations, 
Volta  offered  the  true  explanation  of  the  observations  of  his  uncle, 
and  by  rational  experiments  supported  it  against  powerful  opposition. 
Voltaism  would,  therefore,  seem  to  be  a  more  just  term  for  the 
science  than  galvanism. 


ELECTRICITY  OF  CHEMICAL  ACTION.  Ill 

160.  Voltaic  Pile. — Volta  sagaciously  reasoned,  that  the 
same  effects  could  be  produced  with  simple  metals  and  a 
fluid,  or  substances  saturated  with  a  fluid.  The  truth  of  this 
conjecture  is  easily  verified,  by  placing  on  the  tongue  a 
silver  coin,  and  beneath  it  a  slip  of  zinc,  or  a  cent  of  copper. 
On  touching  the  edges  of  the  two  metals  so  situated,  we  per- 
ceive a  mild  flash  of  light  and  a  sharp  prickling  sensation, 
or  twinge,  giving  notice  of  the  production  of  a  voltaic  cur- 
rent. Volta  arranged  a  series  of  copper  and  silver  coins  in 
a  pile,  with  cloths  wet  in  a  saline  or  acid  fluid 
between  them.  The  arrangement  is  seen  in 
the  figure.  The  copper  (c)  and  zinc  (z)  alter- 
nate with  the  wet  cloth  between.  The  pile 
begins  with  z  and  ends  with  c.  On  establish- 
ing a  metallic  communication  between  these 
extremes  by  a  wire,  a  current  of  electricity 
flows  in  the  direction  of  the  arrow  on  the 
wire.*  If  one  hand  be  placed  on  each  end 
of  the  pile,  a  shock  will  be  experienced,  simi- 
lar in  some  respects  to  that  from  the  electrical 
machine,  and  yet  very  unlike  it.  If  the  pile  has  many 
members,  on  touching  the  wires  communicating  between  the 
extremes,  the  shock  is  very  intense,  and  a  vivid  spark  will 
be  produced,  which  is  increased  if  points  of  prepared 
charcoal  are  attached  to  the  ends  of  the  wires.  The  con- 
ducting wires  held  together  will  grow  hot,  and  if  a  short 
piece  of  small  platina  wire  is  interposed,  it  will  be  heated 
to  bright  redness.  Such  is  an  outline  of  the  remarkable 
discovery  of  Volta,  whose  pile  was  made  known  to  the 
world  in  1800.  The  principle  involved  in  this  arrangement 
is  unaltered,  although  moie  manageable  and  extensive  forms 
of  apparatus  have  supplied  the  place  of  the  pile. 

160.  What  was  Volta's  reasoning  ?     What  instrument  did  he  in- 
vent, and  when  ?     How  was  it  constructed?     What  is  its  action? 


*  The  terms  fluid  or  current ',  are  used  in  obedience  to  custom;  but 
the  learner  should  remember,  that  the  '  fluid'  is  only  an  ideal  one,  as  we 
have  no  evidence  of  its  existence,  and  the  wire  which  communicates 
the  electrical  influence  does  not  carry  any  fluid,  as  a  pipe  carries 
water.  There  is  not  a  particle  of  evidence  as  to  the  real  nature  of 
the  electrical  excitement  produced  by  the  action  of  acid  water  on 
different  metals.  All  we  know  is,  that  so  long  as  such  action  lasts, 
there  is  a  constant  production  of  an  electrical  excitement  or  influence, 
which  we  call  a  current. 


112 


ELECTRICITY. 


161.  Simple  Voltaic  Circle.  —  A  voltaic  current  is 
established  whenever  we  bring  two  dissimilar  metals,  (as 
copper,  silver,  or  platina,  with  zinc  or  iron,)  into  contact  in 
an  acid  or  saline  fluid.  Thus  if  we  place  a 
slip  of  copper  in  a  glass  of  acid  water,  and  be- 
side it  in  the  same  vessel  a  slip  of  amalga- 
mated* zinc,  as  long  as  the  two  metals  do  not 
touch  there  will  be  no  action,  but  on  touching 
the  upper  ends  of  the  two  slips  of  metal,  a 
vigorous  action  will  commence,  bubbles  of  gas 
will  be  rapidly  given  off  from  the  copper,  while 
the  zinc  will  be  gradually  dissolved  in  the  acid 
water.  This  action  will  be  arrested  at  any  moment,  on 
separating  the  two  metals.  The  end  of  the  zinc  in  the  acid 
is  -f,  or  positive,  and  that  in  the  air  — ,  or  negative;  the 
copper  has  the  reverse  signs.  These  relations  are  expressed 
in  the  figures  by  the  signs  -f  and  — ,  and  by  the  direction 
of  the  arrows  showing  how  the  -f  electricity 
of  the  zinc  passes  to  the  —  of  the  copper  in 
1  the  acid  ;  while  the  bubbles  of  gas  (hydrogen) 
r>  - ^9  /set  free  at  the  +  end  of  the  zinc,  travel  over 
and  are  delivered  at  the  —  of  the  copper. 
The  second  figure  shows  how  the  current 
may  \K  established  by  wires,  without  the  di- 
rect  contact  of  the  slips.  In  this  case  the 
wires  (as  in  the  pile,  160)  carry  the  influence 
in  the  direction  of  the  arrows,  and  the  existence  of  the  current 
and  its  positive  and  negative  characters  may  be  shown  by 
the  effect  produced  by  it  on  a  small  magnetic  needle,  which 


161.  What  is  a  simple  voltaic  circle?  Explain  the  electrical 
relations  of  zinc  and  copper,  in  and  out  of  the  acid.  What  is 
amalgamation?  Is  contact  of  the  metals  in  the  vessel  necessary  ? 
Explain  the  second  figure.  What  determines  the  direction  of  the 
current? 


*  Amalgamated  zinc,  is  zinc  which  has  been  rubbed  over  with 
mercury;  this  is  done  by  dipping  common  sheet  or  cast  zinc  into  a 
dilute  acid,  and  while  the  surface  is  still  being  acted  on,  rubbing  it 
with  mercury,  which  will  at  once  cover  the  surface  with  a  resplen 
dent  surface  of  quicksilver.  Pure  zinc  does  not  need  amalgamation, 
but  all  commercial  zinc  is  impure,  and  the  object  of  the  amalgamation 
is  to  cover  over  the  impurities,  (mostly  iron  and  charcoal,)  and  re- 
duce the  surface  to  perfect  electrical  uniformity,  so  that  it  shall  be 
all  positive,  and  not  a  mixture  of  positive  and  negative. 


ELECTRICITY  OF  CHEMICAL  ACTION. 


113 


will  be  influenced  by  the  wires  carrying  the  current,  just  as 
by  the  magnet ;  being  attracted  or  repelled  according  as  it 
is  above  or  below  the  wire,  and  in  either  case  endeavoring 
to  place  itself  at  right  angles  to  the  conducting  wire,  (166.) 
The  direction  of  the  voltaic  current  (and  of  course  the  + 
or  —  qualities  of  the  metals  from  which  it  is  evolved)  de- 
pends entirely  on  the  nature  of  the  chemical  action  produced. 
Thus,  if  in  the  arrangement  just  described,  strong  ammonia 
were  used,  in  place  of  the  dilute  acid,  all  the  relations  of  the 
metals  and  the  fluid  would  be  reversed,  since  the  action 
would  then  be  on  the  copper.  The  chemical  effects  of  the 
voltaic  circle  will  be  considered  in-  the  chapter  on  chemical 
philosophy.  G.t*y-  |  VAt^? 

162.  The  CopipdAtif^roltaic  Circle.— If^Sh-pkcfe  of  one 
cell,  as  just  described,  we  arrange  scveral/Gf  the  same  sort, 
like  the  three  in  the 

figure,  not  forming 
any  direct  metallic 
communication  be- 
tween the  members 
of  the  same  cell,  but 
only  between  those 
of  different  cells, 
then  we  shall  find 
(attending  to  the  signs  -f  and  — )  that  the  positive  electricity 
of  the  first  copper  will  be  exactly  neutralized  by  the  nega- 
tive of  the  zinc  of  the  next  cell,  and  so  on ;  and  we  shall 
have  at  the  terminal  wires  only  the  same  quantity  of  elec- 
tricity which  we  had  in  a  single  cell ;  all  the  opposite 
electricities  of  the  intermediate  members  being  exactly 
neutralized.* 

163.  Quantity  and  Intensity. — We  learn  the  remarkable 
fact  from  this  statement,  that,  no  matter  how  much  we  may 
increase  the  number  of  the  members  in  the  voltaic  circle,  the 
quantity  of  electricity  passing  in  the  current  is  equal  only 


If  ammonia  were  used,  how  would  it  be  ?  162.  What  is  a  com- 
pound voltaic  circuit?  How  are  the  members  united?  Explain 
the  relations  from  the  signs  -{-  and  — .  What  do  we  thus  dis- 
cover ? 


*  This  form  of  apparatus  was  called  the  crown  of  cups,  (Couronne 
tie  tasses,)  being  arranged  in  a  circle. 
10* 


1H  ELECTRICITY. 

to  that  evolved  by  a  single  cell.  But  the  current  which  has 
passed  through  a  number  of  similar  cells  has  acquired  an 
intensity  exactly  proportioned  to  the  number.  Thus  no 
single  cell,  however  large,  would  ever  afford  electricity  of  a 
tension  sufficiently  high  to  decompose  water,  or  give  the 
slightest  shock  to  the  animal  frame.  Hut  the  increase  of 
size  of  the  individual  plates  will  enable  us  to  produce  much 
greater  effects  of  induced  magnetism,  and  to  accumulate 
heat  to  a  surprising  extent.*  These  effects  are  said  to 
depend  on  the  quantity  of  electricity,  while  the  other  class 
depend  on  greater  intensity  given  to  a  smaller  amount  of 
electricity,  bv  extending  the  series. 

The  electricity  always  Hows,  both  in  simple  and  compound 
circles,  from  the  zinc  to  the  copper,  in  the  fluid  of  the  battery  ; 
and  from  the  copper  to  the  zinc,  out  of  the  battery.  This  is 
important  to  be  remembered,  since  the  zinc  is  called  the 
electro-positive  element  of  the  voltaic  series,  although  out  of 
the  fluid  it  is  negative ;  and  consequently,  in  voltaic  decom- 
position, that  element  which  goes  to  the  zinc  pole  is  called 
the  electro-positive  element,  being  attracted  by  its  opposite 
force;  while  the  clement  going  to  the  copper  is  called,  for 
the  same  reason,  the  elcctro-negatire.  The  compound 
circle,  reduced  to  the  simplest  form  of  expression,  would 
be — 

Copper — zinc — -fluid — copper — zinc. 

Here  the  copper  end  is  negative  and  the  zinc  positive 
but  the  two  terminal  plates  are  in  no  way  concerned  in 
the  effect ;  so  that,  throwing  them  out  of  the  question, 
we  bring  it  to  the  state  of  the  simple  circle,  which  is 
simply — 

Zinc — -fluid — copper  ; 

and  here  we  find  the  zinc  end  negative,  and  the  copper  end 
positive. 


163.  Explain  what  is  meant  by  quantity  and  intensity.  What  ad- 
vantage is  there  in  multiplying  the  series,  if  no  more  electricity  is 
evolved  ?  What  happens  from  the  use  of  large  plates  ?  How  does 
the  current  always  flow  in  the  battery  ?  How  out  of  it  ?  What 
electrical  names  then  have  the  copper  and  zinc  ?  Reduce  the  com- 
pound circle  to  its  simple  form  of  expression. 


*  Hare's    calon'motor,    or    heat-mover,    is    constructed     on    this 
principle. 


ELECTRICITY  OF  CHEMICAL  ACTION. 


164.  Galvanic  batteries  are  very  various  in  form,  but  all 
involve  the  same  principle.  Besides  those  already  men- 
tioned, we  may  briefly  name  a  few  others;  and,  (1,)  Mr. 
Cruickshank's,  called  the 
"  trough  battery,"  is 
formed  of  double  plates 
of  copper  and  zinc  sol- 
dered together,  and  cemented  into  a  mahogany  trough,  so 
ns  to  form  a  series  of  tight  cells,  into  which  the  acid  fluid  is 
poured ;  the  effect  is  greatest  at  the  first  moment  of  contact 
of  the  acid  and  plates, 

+ 


and  the  operator  must 
hasten  to  complete  his 
experiments  before  the 
power  has  materially  de- 
clined. (2.)  To  avoid 
this  inconvenience,  Dr. 
Wollaston  contrived  the 
annexed  arrangement, 
where  the  copper  is  bent 
so  as  to  surround  the 
zinc,  thus  doubling  the 
surface  compared  with 
the  last;  the  metallic 
connections  are  made  to  a  bar  of  wood,  by  means  of  which 
the  whole  series  may  be  easily  raised  and  lowered,  in  the 
porcelain  or  earthen-ware  trough,  having  a  separate  cell  for 
each  pair. 

(3.)  Dr.  Hare,  of  Philadelphia,  first  informed  us  that 
separate  cells  were  not  required  for  each  pair  of  plates,  and 
that  by  packing  an  arrangement  similar  to  Wollaston's,  in  a 
frame,  with  varnished  paste-boards  between  the  members, 
to  prevent  any  metallic  contact,  a  large  number  of  members 
might  be  instantaneously  immersed  and  raised  again  from 
the  acid  fluid  at  one  movement.  The  greatest  economy  of 
power  is  thus  gained,  and  the  effects  are  truly  surprising. 
Such  an  arrangement  is  called  a  deflagrator,  from  the  energy 
with  which  it  deflagrates  or  burns  the  metals  and  other 
combustible  substances.  There  is  a  battery  of  this  kind  in 
the  Laboratory  of  Yale  College,  consisting  of  nine  hundred 


164.  Mention  some  of  the  forms  of  battery.     (I.)  Cruickshanks', 
and  its  disadvantages.     (2.)  Wollaston's  improvement. 


116  ELECTRICITY. 

members,  4-X12  inches,  each  zinc  being  surrounded  by  a 
copper  case,  and  the  whole  packed  as  above  described  in 
twelve  frames,  and  all  immersed  at  one  movement.  The 
fluid  used  to  excite  this  battery  is  usually  dilute  sulphuric 
acid,  (1  part  acid  to  14  or  16  of  water  by  weight.)  Its 

deflagrations  are  ex- 
tremely splendid  and 
energetic,  and  the  arch 
of  light  (A  in  the  an- 
nexcd  figure)  given 
out  at  its  poles,  be- 
tween points  of  char- 
coal, (C  C,)  has  often  been  five  or  six  inches  in  length.  The 
power  of  such  an  instrument  in  chemical  decomposition  is 
very  great. 

There  are  many  other  forms  of  voltaic  battery,  but  wo 
have  not  space  to  mention  any  more,  except  those  which 
will  be  named  when  we  treat  of  the  chemical  effects  of 
galvanism.  As  more  knowledge  of  chemical  terms  than  the 
student  is  now  supposed  to  possess  would  be  required  to 
make  them  intelligible,  they  arc  described  under  the  head  of 
chemical  philosophy. 

165.  Effects   of    Voltaic    Electricity. — These   are   con- 
veniently  classified    under    the    heads,   (1,)  Electrical,  (54,) 
Luminous,  (3,)  Calorific,  (4,)  Electro-magnetic,  (5,)  Chemi- 
cal, (6,)  Physiological.     Of  these,  the  first  three  and  the  last 
have  received   as   much  attention   as  our   limits  will  permit. 
The  fifth  will  1*3  considered  alVr  we  have  become  somewhat 
familiar   with   the  principles   of  chemical    philosophy.      We 
have  then   to  consider,  briefly,  the   fourth   effect  of  voltaic 
electricity, 

Electro- Magnetism. 

166.  If  a   wire  conveying  a   voltaic   current   is  brought 
above,  and  parallel  to,  a  magnetic  needle,  (as  shown  in  figure 
a,)  the   latter  is  invariably  affected,  as  if  the  poles  of  another 
magnet   had  been  brought  near,   (130.).     If  the   current  is 


(3.)  Hare's  deflagrators,  and  their  great  superiority.  165.  How 
are  the  effects  of  voltaic  electricity  classed  ?  166.  How  is  the  mag- 
netic needle  affected  by  the  voltaic  current  ? 


ELECTRO-MAGNETISM. 


117 


flowing,  as  indicated  by  the  arrow  on  the 
wire,  say  to  the  north,  then  the  north  pole 
of  the  needle  will  turn  to  the  east;  if 
the  current  is  flowing  south,  it  will  turn  to 
the  west.  If  the  line  carrying  the  current 
is  placed  beneath  the  needle,  the  same  effect 
is  produced  as  if  the  current  had  been  re- 
versed ;  the  needle  turns  in  the  opposite 
way  to  what  it  does  when  the  wire  is  ° 

above.  The  effort  of  the  needle  is  to  place  itself  at  right 
angles  to  the  wire,  as  if  influenced  by  a  tangential  force. 
If  the  wire  is  bent  in  a  rectangle,  as  in 
figure  6,  and  wound  with  silk  or  cot- 
ton, to  prevent  metallic  contact,  and 
the  lateral  passage  of  the  current 
from  wire  to  wire,  then  it  is  evident 
that  any  current  which  may  be  flowing 
over  the  wire  will  have  to  pass  com- 
pletely around  the  needle,  and  the  effect  which  is  produced 
will  be  in  proportion  to  the  number  of  turns  made  by  the 
wire,  since  its  influence' is  multiplied  by  the  number  of  turns. 
In  this  way  we  can  make  a  very  feeble  current  give  decided 
indications.  Prof.  (Ersted,  of  Copenhagen,  in  1819,  first  made 
known  the  law  of  electro- magnetic  attraction  and  repulsion  ; 
since  which  time  the  progress  of  this  branch  of  science  has 
been  very  rapid. 

167.  Galvanoscopes,  or  (Galvanometers,  are  instruments 
by  which  we  measure  the  force  and  direction  of  a  galvanic 
or  voltaic  current,  which  is  often  a  most 
important  thing  to  be  known.  The  prin- 
ciple of  the  last  arrangement  is  here  ap- 
plied. In  order  to  free  the  magnetic 
needle  from  the  directive  tendency  which 
it  receives  from  the  earth's  magnetism, 
two  needles  are  used,  with  their  unlike 
poles  placed  opposite  to  each  other,  (see 
fig.  a,)  one  within  and  the  other  above 
the  coil.  They  will  then  hang  suspended 
by  the  silk  fibre  which  supports  them, 


What  is  the  effect  of  the  needle  ?  If  the  wire  is  bent  into  a  rect- 
angle, what  is  the  effect  ?  Who  discovered  the  first  law  of  electro- 
magnetism,  and  when  ?  167.  What  are  galvanoscopes  ? 


118  ELECTRICITY. 

with  no  tendency  to  swing  in  any  direction,  since  they  are 
wholly  occupied  with  their  own  attractions  and  repulsions, 
and  their  directive  power  is  neutralized ;  consequently,  they 
are  free  to  move  with  the  slightest  in- 
fluence of  any  current  passing  through 
the  coil.  Such  an  arrangement  is  called 
an  astatic  needle.*  To  give  it  greater 
delicacy,  and  prevent  the  currents  of  air 
from  moving  it,  a  glass  shade  (fig.  b) 
is  placed  over  it,  and  the  movements  of 
the  needle  arc  read  on  the  graduated 
circle.f  For  the  purpose  of  elementary 
explanation  of  the  principles  of  electro- 
magnetism,  such  a  needle  as  that  figured 
in  the  last  section  will  answer.  The 
tendency  of  the  galvanometer-needle, 
it  will  be  remembered,  is  always  to 
place  itself  at  right  angles  to  the  direc- 
tion of  the  electrical  current,  that  position  being  the  equator 
of  the  attracting  and  repelling  powers,  and  consequently  a 
point  of  equilibrium. 

168.  Am^re's  Theory. — The  discovery  of  the  first  law 
of  electro-magnetic  influence  by  (Ersted,  attracted  great 
attention;  and  in  1820,  M.  Ampere,  a  French  philosopher, 
made  the  suggestion  that  the  magnetism  of  the  earth  was  due 
to  the  influence  of  the  sun's  rays,  which,  falling  on  the  earth, 
might  be  considered  as  encircling  it  in  an  unending  series  of 
spiral  lines,  producing  in  it  the  phenomena  of  magnetic  in- 
duction, (140.)  The  discovery,  by  CErsted,  of  the  magnetic 
influence  of  an  electric  current,  (166,)  led  him  to  conjecture, 
that  if  such  a  current  was  made  to  pass  in  a  spiral  about  any 
conductor,  it  would  become  magnetic.  This  idea  led  to  the 
discovery  of  the  phenomena  of  the 

1G9.  Helix.\ — A  wire  coiled  in  the  form  here  represented, 


Explain  the    figures.     What   is   an   astatic   needle  ?     168.  State 
Ampere's  theory. 


*  From  the  Greek,  astatox,  just  balanced. 

f  It  was  a  galvanometer  such  as  this  which  was  referred  to  as  being 
used  in  Melloni's  apparatus,  (104.) 

t  So  called  from  the  Greek,  kelisso,  to  twist  round  ;  Latin,  helix, 
in  allusion  to  the  coiling  of  a  vine  about  a  tree. 


ELECTRO-MAGNETISM. 


119 


and  made  the  medium  of  communication  for  a  voltaic  current, 
becomes  capable  of  manifesting 
very  strong  magnetic  influence 
on  any  conductor  placed  in  its 
axis.  A  delicate  steel  needle, 
laid  in  the  helix,  will  be  drawn 
to  the  centre  and  held  suspended 
there,  without  material  support,  like  Mahomet's  fabled  coffin. 
If  the  needle  is  of  steel,  the  magnetism  it  thus  receives  will 
be  retained  by  it ;  but  if  it  be  of  soft  iron,  it  is  a  magnet  only 
while  the  current  is  passing ;  brass,  lead,  copper,  or  any 
other  metallic  conductor,  can  in  this  way  be  made  to  mani- 
fest temporary  magnetic  power.  The  more  closely  the  helix 
is  wound,  and  the  more  revolutions  it  makes,  the  more  pow- 
erful is  the  magnetism  which  it  can  induce,  (166.)  It  is 
essential  that  the  wire  of  which  it  is  formed  should  be  insu- 
lated from  contact  with  itself,  by  being  wound  with  silk  or 
cotton,  or  coiled  in  an  open  spiral,  as  in  the  figure.  A  short 
and  stout  wire  of  lead  or  copper,  connecting  the  poles  of  a 
single  cylinder  battery,  when  excited,  becomes  strongly 
magnetic,  as  may  be  seen  by  the  bundle  of  iron-filings  which 
it  will  then  attract;  each  filing  becomes  itself  a  magnet,  and 
the  whole  surround  the  wire  in  a  beautiful  tuft  or  festoon. 
The  moment  the  connection  between  the  poles  is  broken, 
they  all  fall,  and  the  wire  has  not  power  to  lift  a  single  par- 
ticle of  iron. 

170.  De  la  Rive's  Ring.— We  infer,  therefore,  that  the 
helix  itself  has  polarity,  and  this  is  beautifully  proved  by  the 
arrangement  represented  in  the  an- 
nexed figure,  called  De  la  Rive's 
ring,  which  is  simply  a  small  wire 
helix,  whose  ends  are  attached  to  the 
little  battery  of  zinc  and  copper  con- 
tained in  a  glass  tube,  and  the  whole 
made  to  float  on  the  surface  of  a 
basin  of  water,  by  means  of  a  large 
cork,  through  which  the  glass  tube  is  thrust.  On  exciting 
this  small  battery  by  a  little  dilute  acid,  poured  into  the 


169.  What  discovery  did  Ampere's  theory  lead  to  ?  What  is  a 
helix,  and  its  action?  How  does  a  stout  wire  in  the  poles  of  a  bat- 
tery show  the  spiral  or  tangential  direction  of  the  current? 
170.  What  does  De  la  Rive's  ring  show  ?  Explain  it. 

If 


120  ELECTRICITY'. 

tube,  and  placing  the  apparatus  on  the  water,  it  will  at  once 
assume  a  polar  direction,  as  if  it  were  a  compass-needle,  the 
axis  of  the  helix  being  in  the  magnetic  meridian  ;  and  it  will 
then  obey  the  influence  of  any  other  magnet  brought  near  it, 
manifesting  the  ordinary  attractions  and  repulsions.  _V-*"" 
171.  Electro-magnets, — We  may  avail  ourselves  of* the 
principle  of  the  helix  to  manufacture  artificial  magnets ;  if 
steel  wires  are  introduced,  as  before  stated,  (169,)  within  the 
helix,  they  become  permanent  magnets,  while  soft  iron  is 
made  only  temporarily  so.  The  position  of  the  poles  may 
be  determined  by  a  little  reflection  from  what  has  been 
already  said.  If  the  helix  is  wound  from  left  to  right,  the 
poles  will  be  the  reverse  of  their  position  if  the  winding  was 
from  right  to  left ;  a  reversal  of  the  direction  of  winding  will 
be  the  same  as  changing  the  poles.  By  reversing  the  wind- 
ing in  the  middle  of  the  helix,  we  shall  establish  two  sets  of 
poles ;  and  if  it  is  twice  reversed,  three  sets  will  be  pro- 
duced, and  so  on ;  we  can  also  reverse  the  polarity  of  our 
magnet  at  will,  by  changing  it  end  for  end  in  the  helix,  or 
by  reversing  the  direction  of  the  current. 
Obvious  as  was  the  conclusion  to  which 
these  principles  lead,  Prof.  Henry,  of  Prince- 
ton, was  the  first  who  attempted  to  apply  them 
to  the  production  of  large  magnets,  from  soft 
iron  wound  with  successive  short  coils  of 
covered  wire,  as  in  the  figure.  In  this  way, 
he  succeeded  in  producing  the  most  powerful 
magnets  which  have  been  made.  One  on 
his  plan,  now  in  the  Laboratory  of  Yale 
College,  has  lifted  2500  pounds.  In  these 
magnets  the  wire  is  insulated,  and  wound  in 
short  coils  of  60  to  100  feet,  the  opposite 
ends  of  which  are  connected  with  the  oppo- 
site poles  of  the  battery.  A  small  battery 
was  used  in  one  of  his  experiments,  consisting  of  two  con- 
centric cylinders  of  copper  soldered  into  a  cup,  to  hold  half 
a  pint  of  dilute  acid,  with  a  zinc  cylinder  immersed  in  it. 
With  this,  650  pounds  were  sustained  by  the  magnetism 
induced  in  a  bar  of  soft  iron,  two  inches  square,  twenty 


171.  How  is  the  principle  of  the  helix  applied  to  making  artificial 
magnets  ?  If  the  helix  is  reversed  ?  If  twice  reversed  ?  Mention 
Prof.  Henry's  magnets.  Hour  much  have  they  been  made  to  lift  ? 


ELECTRO-MAGNETISM. 


121 


inches  long,  and  bent  into  the  horse-shoe  form.  This  was 
wound  with  540  feet  of  insulated  copper  bell-wire,  in  nine 
separate  coils  of  60  feet  each.  With  a  larger  battery,  the 
same  magnet  sustained  750  pounds.  A  very  small  electro- 
magnet has  been  made  to  lift  420  times  its  own  weight. 

172.  The  Magic   Circle. — The  reader  must   remember 
that  the  magnetism  of  soft  iron,  induced    from  the  voltaic 
current,  is  not  the  result  of  contact  between 

the  helix  or  coil  and  the  iron  ;  but  this  effect 
is  produced  through  an  intervening  space 
of  air,  or  other  material  which  is  non-con- 
ducting to  ordinary  electricity,  or  galvan- 
ism. The  annexed  figure  shows  two  small 
semicircles  of  soft  iron,  forming  a  ring 
when  united,  and  fitted  with  handles ;  a 
small  coil  of  insulated  wire,  (R,)  placed 
within  the  soft  iron  circle,  will  cause  the 
induction  of  magnetism  in  it,  the  moment 
the  terminal  wires  (a  b)  are  connected 
with  a  small  battery.  The  rings  of  iron 
and  of  wire  are  quite  distinct,  and  may  be 
moved  about  in  each  other ;  the  soft  iron 
semicircles  seem  bound  together  as  if  by 
magic,  and  hence  the  apparatus  has  been 
called  the  magic  circle.  Fifty  or  sixty 
pounds  are  easily  sustained  by  such  an 
apparatus  made  of  iron  about  half  an  inch 
in  diameter. 

173.  Electro-Magnetic    Motions. — The    great    magnetic 
power  induced   in   soft  iron,  early  suggested   its  application 
to  the  moving  of  machinery.     As   yet,   however,  we  have 
produced   nothing   which  can   take  the  place  of  steam  or 
water,  as  a  moving   power.     The  causes   of  failure   cannot 
well  be  explained  in  this  place,  as  they  involve  some  chemical 
reasoning  which  would  be  in  anticipation  of  our  knowledge. 

Faraday  was  the  first  who  succeeded  in  producing  mo- 
tion by  the  mutual  action  of  magnets  and  conductors.  It  is 
quite  impossible  to  name,  much  less  describe,  even  a  tenth 


172.  Is  electro-magnetism  the  result  of  contact  ?  Illustrate  this 
from  the  magic  circle.  173.  Has  the  great  power  of  electro-magnets 
been  made  available  for  use  ?  Who  first  produced  electro-magnetic 
motion  ?  • 

11 


122 


ELECTRICITY. 


part  of  the  ingenious  and  instructive  forms  of  apparatus 
which  have  been  contrived  by  various  experimenters,  for 
producing  motion. 

Ampere's  Rotating  Battery  is  an  instructive  form  of  appa- 
ratus, and  one  of  the  first  contrived. 
In  this,  a  small  double  cylinder  or  cup 
of  copper  is  hung  by  a  pivot  over  and 
around  the  pole  of  a  U  magnet,  standing 
as  represented  in  the  sectional  figure  on 
pole  S.  This  holds  the  dilute  acid,  into 
which  the  zinc  cylinder  (Z)  dips,  which 
is  suspended  on  another  pivot  so  as  to 
hang  freely.  As  soon  as  the  acid 
water  is  poured  into  the  cup,  a  current 
of  electricity  will  flow  (161)  from  ihc 
zinc  to  the  copper,  over  the  wire  and 
through  the  pivot  to  the  zinc  again. 
The  zinc  and  copper  are  in  the  con- 
dition of  two  conductors,  conveying 
an  electric  current  in  opposite  direc- 
tions, and  being  under  the  influence 
of  the  poles  of  the  magnet,  (166,)  and 
free  to  move,  they  revolve  in  opposite 
directions.  If  each  pole  is  thus  provided,  the  cups  and  zincs 
on  each  will  revolve  difFerently. 

174.  Page's  Revolving  Armature* — One  of  the  simplest 
forms  of  the  electro-magnetic  engine  is  that  figured  on  the 
next  page,  in  which  an  electro-magnet  (M)  is  fixed  on  a  stand, 
with  its  poles  in  an  upright  position.  A  brass  wheel  is  so 
placed  over  it,  that  three  bars  or  armatures  of  soft  iron,  (A,) 
which  divide  the  circumference,  may  pass  very  near  to  the 
poles  of  the  magnet,  as  the  wheel  turns.  The  arrangement 
is  such,  that  the  revolution  of  the  wheel  shall  break  the 

Describe  Ampere's  rotating  battery.  174.  What  is  Page's  re- 
volving armature,  and  how  does  it  operate  ? 


•Dr.  C.  G.  Page  of  the  Patent  Office,  Washington,  is  the  author  of 
numerous  ingenious  electro-magnetic  machines,  [for  an  account  of 
which  see  the  American  Journal  of  Science,  passim,]  and  is  one  of  the 
most  successful  cultivators  of  this  science.  His  apparatus,  with 
much  other  useful  matter,  will  be  found  described  and  figured  in  a 
useful  work  called  Davis's  Manual  of  Magnetism,  18mo.  Boston, 
1842.  Several  of  the  figures  here  given  are  from  Mr.  Davis's  book. 


ELECTRO-MAGNETISM. 


123 


connection  between  the  battery  and  the  electro-magnet, 
three  times  in  every  revolution.  Tin's  is  accomplished  by 
the  wire  (B)  which  plays  upon  three 
pins  of  wire,  in  the  little  disc  seen 
upon  the  horizontal  axis  of  the 
wheel.  As  often  as  these  pins 
touch  the  wire,  (B,)  the  circuit  is 
completed,  and  the  soft  iron  (M) 
becomes  a  magnet.  As  soon,  how- 
ever, as  this  contact  is  broken,  M 
ceases  to  be  a  magnet.  Now  this 
happens  three  times  in  every  revo- 
lution of  the  wheel,  and  the  breaking 
of  contact  is  so  contrived  that  it 
always  happens  just  when  one  of 
the  soft  iron  armatures  (A)  comes 
over  the  poles  of  the  electro-magnet. 
The  bars  (A)  being  each  in  suc- 
cession strongly  attracted  to  the 
poles  of  the  magnet,  cause  the  wheel 
to  move,  and  the  revolution,  being 
once  established,  is  kept  up  with 
great  velocity.  If  the  magnetism  in 
M  was  not  destroyed  by  the  contact- 
breaker,  (B,)  at  the  very  time  when  A  comes  over  the  poles 
the  revolution  would  be  arrested  by  the  strong  attraction  of 
4hc  magnet  for  the  armature. 

175.  Henry1  s  Coils. — When  an  electrical  current  from 
a  single  pair  of  plates  is  passed  through  a  long  conductor, 
as  a  spiral  of  copper  ribbon,  or  a  long  bell-wire,  it  will  be 
found,  at  the  moment  of  breaking  the  contact  between  the 
conductor  and  the  battery,  that  vivid  sparks  will  appear,  and 
a  feeble  shock  will  be  felt  if  the  moistened  fingers  grasp  the 
naked  conductors. 

A  long  conductor  then  supplies  the  place  of  an  increased 
number  of  plates  in  a  voltaic  series,  and  to  some  degree 
imparts  the  quality  of  intensity  (163)  to  a  current  of  quan- 
tity. A  flat  spiral  of  copper  ribbon  one  hundred  feet  long, 
wound  with  cotton,  and  varnished,  shows  these  effects  well. 
A  magnetic  needle  will  be  powerfully  affected  by  this  coil 
while  the  current  is  passing ;  the  N.  or  S.  pole  being  drawn 


175.  What  is  the  effect  of  Henry's  coils  on  the  voltaic  current  ? 


124  ELECTRICITY. 

toward  the  centre,  (see  the  figure,)  according  to  the  direction 
of  the  current,  the  reversal  of  the 
current  producing  a  reversal  in  the 
direction  of  the  needle.  The  oppo- 
site sides  of  the  spiral  of  course 
produce  opposite  eflects  on  the 
needle.  Its  axis,  it  will  be  seen,  is 
the  same  as  that  of  the  helix, 
(169,)  and  it  will  in  like  manner 
produce  magnetism.  The  mag- 
netism  is,  however,  to  be  distin- 
guished from  the  new  effects  excited  by  the  passage  of  the 
feeble  current  through  the  coiled  conductor,  on  breaking  con- 
tact, i.  e .,  the  vivid  spark  and  the  shock.  The  latter  is  feeble 
with  100  feet  of  copfHT  ribbon,  and  becomes  more  intense 
(178)  if  the  length  of  the  conductor  l>e  increased,  the  battery 
remaining  the  same ;  but  the  sparks  are  diminished  by 
lengthening  the  conductor.  The  increase  of  intensity  in  the 
shock  is,  however,  limited  by  the  increased  resistance  or 
diminished  conduction  of  the  wire,  which  finally  counteracts 
the  influence  of  the  increasing  length  of  the  current.  On  the 
other  hand,  if  the  battery  power  be  increased,  the  coil  remain- 
ing the  same,  these  actions  diminish.  This  class  of  phe- 
nomena has  been  attributed  to  the  induction  of  a  current 
upon  itself.  Prof.  Henry  first  observed  the  eflects  here 
described,  and  has  made  an  extended  series  of  researches  on 
this  species  of  induction,  as  well  as  that  mentioned  in  the  next 
section. 

176.  Secondary  Currents. — If  a  long  coil  of  fine  insulate^ 
wire  be  brought  within  a  small  distance  of  the  flat  spiral, 
figured  in  the  last  section,  a  new  species  of  induction  will  be 
detected  in  the  coil  of  fine  wire.  The  arrangement  used  by 
Prof.  Henry  is  seen  in  the  annexed  figure.  A  small  sus- 
taining battery  (L)  is  connected  with  the  flat  spiral  of  copper 
ribbon,  (A,)  by  wires  from  the  battery  cups,  (Z  and  C.) 
This  communication  is  broken  at  will,  by  drawing  the  end 
of  one  of  the  battery  wires  (Z)  over  the  rasp  on  the  spiral. 
When  the  coil  of  fine  wire  (W)  is  in  the  position  indicated 

What  does  the  long  conductor  imitate  ?  How  is  the  magnetic 
needle  affected  by  the  flat  spiral  ?  How  are  the  two  effects  of  shock 
and  spark  related  to  the  length  of  the  conductor  ?  To  what  are 
these  effects  attributable  ?  176.  What  are  secondary  currents  ? 
Explain  the  arrangement  here  figured,  and  the  effects. 


ELECTRO-MAGNETISM. 


125 


in  the  figure,  and  the   hands  grasp  the  conductors  at  the  ex- 
tremities, a  violent  shock  is   felt   by  the   person   holding  the 


conductors,  as  often  as  the  circuit  is  broken  by  the  passage 
of  the  wire  over  the  rasp.  When  the  coil  (W)  contains 
several  thousand  feet  of  wire,  the  shocks  are  too  intense  to 
be  borne.  As  this  induction  takes  place  through  an  inter- 
vening space  of  air,  or  non-conductors,  we  can,  by  placing 
the  spiral  (A)  against  a  division-  wall  or  the  door  of  a  room, 
give  shocks  to  a  person  in  another  room,  who  grasps  the 
conductors  of  the  wire  coil,  (W,)  arid  brings  it  near  to  the 
wall  on  the  side  opposite  to  A.  This  effect  is  produced 
as  if  by  magic,  without  a  visible  cause.  A  screen  or  disc 
of  metal  introduced  between  the  two  coils  will  cut  off  this 
inductive  influence,  by  itself  becoming  the  medium  of  an  in- 
creased current.  But  if  it  be  slit  by  a  cut  from 
the  centre  to  the  circumference,  as  a  b  in  the 
figure,  the  induction  of  an  intense  current  in  W 
is  the  same  as  if  no  screen  were  present.  Discs  or  screens 
of  wood,  glass,  paper,  or  other  non-conductors,  offer  no  im- 
pediment to  this  induction. 

177.  Induced  currents  of  the  third,  fourth,  and  fifth 
order. — If  the  wires  from  W  be  connected  with  another  flat 
spiral,  and  it  with  a  second  coil  of  fine  wire,  and  so  on,  a 
series  of  currents  will  be  induced  in  each  alternation  of  coils. 
The  secondary  intense  current  in  B,  will  induce  a  quantity 
current  in  the  second  flat  spiral,  (C ;)  and  a  second  fine  wire 
coil  (W)  will  induce  a  tertiary  intense  current,  and  so  on. 
These  currents  have  been  earned  to  the  ninth  order,  de- 
creasing each  time  in  energy  by  every  removal  from  the 


When  is  the  shock  felt  by  the  person  holding  the  ends  of  the  fine 
wire  ?  What  magical  modification  of  the  experiment  is  mentioned  ? 
How  do  screens  of  metal  affect  the  induction  ?  How,  if  they  are 
slit  ?  How,  if  of  non-conducting  substances  ? 


126 


ELECTRICITY. 


original  battery  current.     The  polarity,  or  direction  of  these 
secondary   currents,  alternates,   commencing   with    the  sec- 


ondary.  Thus  the  current  ot  the  battery  is  -f  ;  and  the 
.secondary  current  is  -f  ;  the  current  of  the  third  order  is  —  ; 
the  current  of  the  fourth  order  is  -}-  ;  and  the  current  of  the 
fifth  order  is  —  .  These  alternations  are  marked  in  the  figure 
above. 

173.  Compound  Electro-magnetic  Machine. — Hy  com- 
bining and  modifying  the  results  just  briefly  enumerated,  a  great 
numljcr  of  ingenious  and  beautiful  electro-magnetic  machines 
have  been  produced,  founded  on  the  principle  of  the  flat  spiral, 
secondary  intense  currents,  nnd  induced  magnetism.  One  of 

these,     contrived     by 
r  Or.    Page,   is    figured 

in  the  margin.  In 
this  little  machine,  a 
short  coil  of  stout  in- 
sulated copper  \\ire 
forms  a  helix,  within 
which  some  straight 
soft  iron  wires  (M) 
are  placed.  The  bat- 
tery current  is  made  to  pass  through  this  stout  wire,  by  which 
'means  magnetism  is  induced  (1C9)  in  the  soft  iron.  The 
conducting  wires  are  so  arranged  beneath  the  board,  that  the 
glass  cup  (C)  containing  some  mercury  is  in  connection  with 
the  battery.  Tho  bent  wire  (W)  dips  into  this  mercury,  and 
also  by  a  branch  into  B,  and  when  in  the  position  shown  in 


177.  Explain  the  induced  currents  of  the  third,  fourth,  and  fifth 
order,  and  their  several  polarities.  178.  How  are  the  principles  of 
175  and  176  combined  in  the  instruments  here  figured  ?  Where  ia 
the  magnetism  ? 


ELECTRO-MAGNETISM.  127 

the  figure,  the  current  from  the  battery  will  flow  uninter- 
ruptedly. As  soon,  however,  as  the  battery  connection  is 
completed,  M  becomes  strongly  magnetic,  and  draws  to  itself 
a  small  ball  of  iron  on  the  end  of  P;  this  moves  the  whole 
wire  (P  W)  and  raises  the  point  out  of  the  mercury,  (C;)  as 
the  wire  leaves  the  mercury,  a  brilliant  spark  is  seen  on  its 
surface,  (176;)  the  contact  being  thus  broken  with  the  bat- 
tery, M  ceases  to  receive  induced  magnetism,  and  the  ball 
(P)  being  consequently  no  longer  attracted  to  M,  the  wire 
(VV)  falls  by  its  gravity  to  the  position  in  the  figure.  This 
again  establishes  the  battery  connection,  and  the  same  effects 
just  described  recur;  thus  the  bent  wire  (W)  receives  a 
vibratory  motion,  and  at  each  vibration  a  brilliant  spark  is 
seen  at  C,  and  M  becomes  magnetic.  It  remains  only  to 
mention  that  the  short  quantity  wire  is  surrounded  by  a  fine 
intensity  wire,  2000  to  3000  feet  long,  having  no  metallic 
connection  with  the  battery  or  quantity  wire,  with  its  ends 
terminating  in  two  binding  screws  on  the  left  of  the  board. 
The  fine  wire  receives  a  secondary  induced  current  like  the 
coil,  (W,  176,)  which,  if  touched,  produces  the  most  intense 
shocks  at  each  vibration  of  the  wire. 

179.  The  filectro-inagnctic  telegraph  is  a  contrivance 
which  very  happily  illustrates  the  application  of  abstract 
scientific  principles  and  discovery  to  the  wants  of  society. 
The  inconceivably  rapid  passage  of  an  electrical  current  over 
a  metallic  conductor,  was  discovered  by  Watson  in  1747, 
and  this  discovery  gave  the  first  hint  of  the  possibility  of 
using  electricity  as  a  means  of  telegraphic  communication. 
Numerous  attempts  were  made  very  early  after  this  discovery 
to  construct  a  telegraph  to  be  worked  by  ordinary  electricity, 
but  from  difficulties  inherent  in  the  mode,  these  attempts  were 
attended  with  only  very  partial  success.  The  discovery  of 
electro-magnetism  by  Oersted,  in  1820,  (166)  supplied  the 
necessary  means  of  successful  construction.  Many  plans 
have  since  been  proposed  for  accomplishing  this  object,  most 
of  which  have  failed  from  a  want  of  simplicity  in  construction 
and  notation,  and  from  consequent  inefficiency.  Superior  to 
all  others  in  these  essential  conditions  of  success,  is  the  beau- 
tiful contrivance  patented  by  Prof.  Morse  in  1837,  which  we 
will  now  briefly  describe. 

When  is  the  spark,  and  when  the  shocks  1  179.  What  suggested 
the  electrical  telegraph  ?  What  discovery  gave  the  means  of  success  ? 


128 


ELECTRICITY. 


The  successful  operation  of  the  electric  telegraph  depends 
on  the  fact,  that  an  electro- magnet  can  be  created  ut  any 
point,  no  matter  how  distant  from  us,  provided  a  good  metallic 
communication  is  established  by  conducting  wires  between 
the  battery  and  the  distant  station.  There  is  no  difficulty  in 
understanding  how  the  power  of  the  battery  on  our  table  may, 
by  long  wires,  be  made  to  move  any  electro-magnetic  ma- 
chine on  the  other  side  of  the  room,  or  in  an  adjoining  apart- 
ment. We  have  only  to  extend  this  idea  to  places  distant 
from  each  other,  100,  or  1000,  or  10,000  miles,  and  we  have 
a  conception  of  the  magnetic  telegraph.  The  machinery 
required  is  of  the  simplest  kind.  In  the  accompanying  figure 


we  have  a  view  of  its  most  essential  parts.  It  is  called  the 
telegraphic  register.  A  simple  electro-magnet,  (m  m,)  with 
its  poles  upward,  receives  its  induced  magnetism  (171)  from 
n  current  of  electricity  conducted  by  the  wires  (W  W)  from 
the  distant  station.  Suppose  that  the  battery  which  excites  this 
current  is  in  Washington,  and  the  electro-magnet  is  in  Boston. 
As  soon  as  the  circuit  is  completed  by  the  union  of  the  poles 
in  Washington,  m  m  becomes  a  magnet,  and  draws  to  its 
poles  an  armature  or  bar  of  soft  iron  (a)  on  the  lever,  (/.) 
The  motion  of  this  lever  starts  a  spring  which  sets  in  motion 
the  clock  arrangement,  (c.)  This  clock  machinery,  in  con- 
sequence of  the  weight  attached  to  it,  will,  when  once  set  in 

On  what  does  the  operation  of  the  telegraph  depend  ?     Explain  the 
apparatus  as  here  figured. 


ELECTRO-MAGNETISM.  129 

motion,  continue  to  move.  As  soon  as  it  begins  to  move,  the 
bell  (6)  is  rung  by  the  machinery,  to  warn  the  superintendent 
that  he  is  about  to  receive  a  communication.  The  immediate 
object  of  the  clock  machinery  is  to  draw  forward  a  narrow 
ribbon  of  paper,  (p  p,)  in  the  direction  of  the  arrows,  and  to 
cause  it  to  advance  with  a  regular  motion.  The  paper  ribbon 
passes  by  the  end  of  the  pen  lever,  (/,)  in  which  is  a  steel 
point,  (s,)  that  indents  the  paper  whenever  this  end  of  the 
lever  is  thrown  upwards  by  the  attraction  of  the  armature  (a) 
to  the  magnet,  (m.)  If  m  m  were  constantly  magnetized,  the 
mark  made  by  the  point  (a)  would  be  a  continuous  line.  Hut 
we  have  before  seen  that  we  can  make  and  discharge  an 
electro-magnet  as  often  and  as  fast  as  we  please ;  the  instant, 
therefore,  the  circuit  (w  tr)  is  broken  by  the  operator  at  the 
battery  in  Washington,  m  m  erases  to  be  a  magnet,  and  lots 
go  the  iron  armature,  (a,)  when  the  point  (s)  of  the  lever 
falls,  so  as  no  longer  to  mark  the  paper.  The  circuit  being 
renewed,  the  point  marks  again ;  and  this  may  be  repeated 
as  often  as  the  operator  at  Washington  pleases.  The  length 
of  time  that  the  circuit  is  closed,  will  be  exactly  registered  in 
the  corresponding  length  of  the  mark  made  by  5.  The  com- 
pleting of  the  circuit  is  performed  by  touching  a  spring  on 
the  operator's  table,  which  establishes  a  metallic  communi- 
cation between  the  poles  of  the  battery.  A  touch  will  pro- 
duce a  dot,  a  continued  pressure  a  long  line,  and  intermitting 
repeated  touches  a  series  of  dots  and  short  lines.  This 
enables  the  operator  to  mark  the  paper  at  Boston  with  :i 
series  of  dots  and  lines,  so  arranged  as  to  form  a  telegraphic 
alphabet,  by  means  of  which  he  can  easily  and  rapidly  com- 
municate his  thoughts.  To  complete  the  arrangement,  the 
operator  in  Boston  must  have  his  own  battery  in  connection 
with  another  similar  register  in  Washington.  In  practice 
only  one  wire  is  used  with  each  register,  the  circuit  being 
completed  by  connecting  the  other  pole  of  the  battery  with 
the  moist  earth  by  means  of  a  buried  metallic  plate  and  a 
wire.  The  remarkable  observation  that  the  earth  could  be 
used  in  this  manner  as  a  part  of  the  circuit,  was  made  by 
Steinheil,  in  Germany,  in  1837.  Such  is  a  brief  account  of 
one  of  the  most  remarkable  discoveries  of  modern  times; 


What  is  the  object  of  the  clock-work  ?  How  does  the  point  mark 
the  paper  ?  What  relation  is  there  between  the  length  of  the  marks 
and  the  battery  circuit  ?  How  are  the  conducting  wires  arranged  ? 


130  ELECTRICITY. 

many  particulars  arc  purposely  omitted,  to  avoid  confusion  in 
the  main  idea.  The  paper  ribbon  (p)  is  supplied  from  a 
large  coil  not  shown  in  the  figure.  This  telegraph  makes  a 
permanent  record  of  the  communication  sent,  and  is  thus 
independent  of  the  presence  or  attention  of  the  attendant. 
If  it  were  possible  to  unite  the  antipodes  by  telegraphic  wires, 
no  measurable  time  would  be  required  to  make  communi- 
cations, such  is  the  inconceivable  rapidity  of  electrical 
currents. 

One  curious  fact  connected  with  the  operation  of  the  tele- 
graph, is  the  induction  of  atmospheric  electricity  upon  the 
wires  to  such  an  extent,  as  often  to  cause  the  machines  at 
the  several  stations  to  record  the  approach  of  a  thunder-storm. 
This  induction  occasions  a  serious  inconvenience  in  working 
the  telegraph,  not  unattended  with  danger  to  the  operators. 
The  electricity  thus  induced  on  the  wires  may,  howevejf,  be 
withdrawn  by  points  of  metal  in  communication  with  the  earth, 
and  placed  at  a  suitable  distance  from  the  conductor. 

180.  Magneto- Electricity. — As  we  have  seen  effects  pro- 
duced from  galvanism,  which  exactly  resemble  those  of  ordi- 
nary machine  electricity,  and  the  magnetic  influence,  so, 
conversely,  we  might  expect  the  production  of  electrical  effects 
from  the  magnet.  The  electrical  current  from  a  single 
galvanic  pair,  we  have  seen,  produces  magnetism  in  a  spiral 
wire  at  right  angles  with  its  own  course ;  so  the  induction  of 
magnetism  in  soft  iron  from  a  permanent  mairnet,  in  like 


What  is  said  of  the  atmospheric  electricity  ?     180.  What  is  mag- 
neto-electricity ? 


THERMO-ELECTRICITY.  131 

manner,  produces  an  electrical  current  at  right  angles  to  itself 
in  the  wire  coiled  on  the  armature.  This  class  of  phenomena 
was  discovered  by  Faraday  in  1831,  and  our  countryman, 
Mr.  J.  Saxton,  soon  contrived  a  machine  very  similar  to  the  ono 
of  which  a  figure  is  here  given,  called  a  Magneto-electrical 
Machine.  This  consists  of  a  powerful  magnet,  (S,)  secured 
to  a  board,  with  its  poles  so  situated  that  an  armature,  formed 
of  two  large  bundles  of  insulated  copper  wire,  (W,)  wound 
on  soft  iron  axes,  may  be  revolved  on  an  axis  before  its  '" 
|K)les,  by  the  multiplying  wheel,  (M.)  A  current  of  electricity 
is  thus  induced  in  VV,  just  as  in  the  flat  coils,  the  permanent 
magnet  here  taking  the  place  of  the  flat  spiral,  (176.)  The 
current  excited  in  VV  is  led  off  by  conductors  to  the  binding 
screws,  (p  and  n,)  the  continuity  of  the  current  being  broken 
(in  imitation  of  the  rasp  in  176)  by  a  contrivance  at 
b  on  the  axis,  called  a  break-piece,  which  is  made  /  ' 
by  alternate  ribs  of  metal  (c)  and  ivory  (i)  as  in  *~ 
the  annexed  figure ;  the  current  is  broken  by  the 
ivory  and  renewed  by  the  metal,  and  at  every  break  the  per- 
son whose  hands  grasp  the  conductors  secured  to  p  and  n 
feels  a  sharp  shock,  which  may  be  graduated  at  will  by  the 
rapidity  of  the  revolutions  of  M,  and  by  the  adjustment  of  the 
break,  (b.)  A  long  and  fine  wire — say  3000  feet  of  wire  fa 
of  an  inch  in  diameter — is  required  to  produce  shocks  and 
chemical  decompositions.  A  shorter  and  stouter  wire,  as  250 
feet  of  wire  fa  or  fa  inch  in  diameter,  will  produce  no  shock, 
but  will  deflagrate  the  metals  powerfully,  and  produce  a 
secondary  current  of  induction  in  soft  iron.  We  thus  imitate  in 
magnetism  the  effects  produced  from  a  voltaic  current,  (163  ;) 
the  short  and  stout  wire  of  the  armature  is  the  simple  circuit 
of  large  plates ;  the  long  and  fine  wire  is  like  the  com- 
pound circuit  of  smaller  plates. 

4.   Thermo-Electricity,   or  the  Electrical  current  excited 
by  Heat. 

181.  If  two  metals  unlike  in  crystalline  structure  and 
conducting  power  are  united  by  solder,  and  the  point  of  their 
union  is  heated  or  cooled,  an  electrical  current  will  be  ex- 


Who  discovered  this  class  of  phenomena,  and  when  ?  What  is 
magneto-electricity  the  converse  of?  Explain  Saxton's  machine. 
Explain  the  relations  of  the  quantity  and  intensity  wire  to  the  simi- 
lar effects  of  the  voltaic  battery. 


132  ELECTRICITY. 

cited,  which  will  flow  from  the  heated  point  to  the  metal 
which  is  the  poorer  conductor.  Bismuth  and 
antimony  are  such  metals,  being  bad  conduc- 
tors, and  unlike  in.  crystalline  structure.  If 
two  bars  of  these  metals  arc  united,  as  in  the 
figure,  and  the  point  (c)  is  warmed  by  a  lamp, 
a  current  will  be  set  in  motion  which  will  flon 
from  b  to  «,  as  in  the  figure.  The  compus: 
needle  may  be  thus  affected,  as  by  the  vol. air 
current,  (166.)  For  this  purpose  two  bars  may  be  merited 
MS  in  the  figure,  and  their  j'.nction 
being  heated  by  a  lamp,  the  needle 
will  swing,  in  eonseqiir.icc  of  the 
electrical  current  oxci'ed  by  the  heat. 
When  several  such  are  joined,  we 
have  a  greatly  in." /eased  effect,  as 
will  be  remcmbcrc'd  in  the  thermo- 
electric pile  in  Melloni's  apparatus,  (1C4.) 

Thermo-electric  effects  are  not  confined  to  metals,  for  they 
may  bo  produced  from  other  solids,  and  even  from  fluids  ;  and 
a  single  metal,  as  an  iron  wire,  which  has  been  twisted  or  bent 
abruptly,  will  originate  a  thermo-electric  current  when  the 
distorted  part  is  greatly  heated.  The  rank  of  the  principal 
metals  in  the  thermo-electric  series  is  as  follows,  beginning 
with  the  positive:  bismuth,  mercury,  platinum,  tin,  lead, 
gold,  silver,  '/inc,  iron,  antimony.  When  the  junction  of 
any  pair  of  these  is  heated,  the  current  passes  from  that 
which  is  highest  to  that  which  is  lowest  in  the  list,  the  ex- 
tremes affording  the  most  powerful  combination. 

If  we  pass  a  feeble  current  of  electricity  through  a  pair  of 
antimony  and  bismuth,  the  temperature  of  the  system  rises, 
if  the  current  passes  from  the  former  to  the  latter  ;  but  if 
from  the  bismuth  to  the  antimony,  cold  is  produced  in  the 
compound  bar.  If  the  reduction  of  temperature  is  slightly 
aided  artificially,  water  contained  in  a  cavity  in  one  of  the 
bars  may  be  frozen.  Thus  we  see  that  as  change  of  tempe- 
rature disturbs  the  electrical  equilibrium,  so  conversely  the 
disturbance  of  the  latter  produces  the  former. 


181.  What  is  thermo-electricity  7  In  what  substances  is  it  ex- 
cited ?  What  metals  are  here  named  ?  Which  way  does  the  current 
flow  ?  Are  these  effects  confined  to  metals  ?  Are  two  metals 
essential  ?  Enumerate  the  order  of  some  metals  producing  thermo- 
electric effects.  What  experiment  is  stated  the  converse  of  the 
foregoing  ? 


CHEMICAL    PHILOSOPHY.  133 

PART  II.— CHEMICAL  PHILOSOPHY. 
I.  ELEMENTS  AND  THEIR  LAWS  OF  COMBINATION. 

182.  Number  and  Classification  of  Elements. — We  have 
already  defined   the   chemical   sense  of  the   word   Element, 
(14,)  and  mentioned  that  there  are  fifty-six  such  substances 
at   present   known  to  us.     There  are  also  several  other  sub- 
stances which  have  been  lately   proposed  as  elements  of  the 
metallic  class, — about  which,   however,  we   know   so   little, 
that  they  are  not   included   in  our   list,  (188.)     About  forty 
of  the  elements  have  the  peculiar  lustre,  and  other  properties 
of  metals,  and  it  is  customary  to  divide  the  elements  into  two 
great  classes — the  metallic  and  the  non-metallic.     This  con- 
venient  distinction  is  not,  however,  strictly  accurate,  since 
there   are  several    elements   which,   like   tellurium,   carbon, 
arsenic,    silicon,    &c.,    seem    to    possess    an    intermediate 
character.     Only  fourteen  of  the  elementary  bodies  are  of 
common  occurrence,  and  of  these  the  atmosphere,  water,  and 
the  great  bulk  of  the  planet  are  composed.     The   remainder 
are  comparatively  rare,  and   are   known  only  to  the  chemist. 
But  the  same   laws  of  combination  apply  to  the  whole,  and 
we  shall  best  accomplish  our  present  object  by  discussing  the 
first  principles  of  chemical  philosophy,  and  illustrating  them 
by  a  selection  of  facts,  rather  than  by  attempting  the  task  of 
giving  too  much  detail. 

183.  State  in  which  the  elements  exist.  —  At  common 
temperatures,  and  when  set   free   from   combination,  nearly 
all   the  elements  are  solids.     Two,  mercury  and   bromine, 
are  fluids,  and  five  are  gases,  namely,   chlorine,   fluorine, 
hydrogen,    oxygen,    and    nitrogen.       A    few    only   of  the 
elements   are   naturally  found  in  a  free  or  uncombined  state, 
among   which    we    may   name    oxygen,    nitrogen,    carbon, 
sulphur,   and    nine  or   ten    metals.     All    the    rest   exist   in 
combination  with  each  other,  and  so  completely  concealed  or 
disguised  as  to  be  known  only  to  the  chemist. 


182.  How  many  elements  do  we  know  ?  How  are  these  usually 
divided  ?  How  many  are  found  as  principal  constituents  of  the 
globe?  183.  In  what  state  do  the  elements  exist?  Which  are 
fluids  ?  Which  are  gases  ?  Which  are  free  or  uncombined  ?  In 
what  state  are  the  others  ? 
12 


134-  ELEMENTS  AND  THEIR  LAWS  OF  COMBINATION. 

1.   Combination  by   Weight. 

184.  The  laws  by  which  the  elements  unite  to  form  com- 
pounds, arc  included  in  the  four  following  propositions. 

1st  LAW.  A  compound  of  two  or  more  elements  is  always 
formed  by  the  union  of  certain  definite  and  unalterable  pro- 
portions of  its  constituent  elements. 

This  is  the  law  of  definite  proportions. 

2d  LAW.  When  two  bodies  unite  in  more  proportions  than 
one,  these  proportions  bear  some  simple  relation  to  each 
other. 

This  is  the  law  of  multiple  proportions. 

3d  LAW.  When  a  body  (A)  unites  with  other  bodies,  (B,  c, 
D,  &c.,)  the  proportions  in  which  H,  c,  and  D,  unite  with  A,  will 
represent  in  numbers  the  proportions  in  which  they  will  unito 
among  themselves,  in  case  such  union  takes  place. 

This  is  the  law  of  equivalent  proportions. 

4th  LAW;  The  combining  proportion  of  a  compound  body 
is  the  sum  of  the  combining  weights  of  its  several  elements. 

This  is  the  law  of  the  combining  numbers  of  compounds. 

These  four  laws  are  the  foundation  of  all  chemical  science, 
and  should  receive  the  attention  which  their  great  importance 
demands.  We  will  briefly  illustrate  their  meaning,  which 
will  be  done,  however,  more  effectually  by  the  constant  use 
we  shall  have  to  make  of  them,  on  almost  every  succeeding 
page  of  this  treatise. 

185.  Definite   Proportions. — Analysis  shows   us  that    a 
given  compound  is  always  formed  of  certain  elements  in  defi- 
nite proportions,  and   that   no  change  can   take   place   in  the 
number  or   proportion   of   its   constituent  elements,   without 
destroying  its   peculiar  character,  and   forming  a  new  sub- 
stance.    Thus,  in  nine  grains  of  water  there  are  eight  grains 
of  oxygen  and  one  grain  of  hydrogen.     Any  attempt  to  form 
water   from  any  other   proportion  of  its  elements  would  be 
useless.     Constancy  of  composition  is  essential  to  the  being 
of  chemical  compounds. 

186.  Multiple  Proportions. — If  a  body  (A)  unites  with  a 
body  (B)  in  more  proportions  than  one,  thus  producing  more 


18 1.  State  the  first  law  of  combination.  What  is  this  law  called  ? 
What  is  the  second  law?  What  is  this  law  called?  What  is  the 
third  law,  and  what  called  ?  The  fourth,  and  what  called  ?  What 
is  said  of  these  laws  ?  185.  What  has  analysis  shown  ?  Illustrate 
this? 


COMBINATION  BY  WEIGHT.  135 

than  one  compound  of  the  two  elements,  these  proportions 
bear  a  simple  relation  to  each  other.  (1.)  We  may  have  a 
series  of  compounds  represented  by  A-j-B  :  A-f  2B  :  A-J-3B  : 
A  +  4B  :  A  +  5B  :  in  which  one,  two,  three,  four,  and  live 
parts  by  weight  of  B,  unite  with  one  part  of  A,  forming  five 
separate  and  distinct  compounds.  Several  examples  of  this 
law  will  be  found  in  the  following  pages.  (2.)  In  place  of 
the  simple  ratio  of  numbers  here  explained,  we  may  have 
another  series  of  compound  bodies,  whose  elements  bear  to 
each  other  an  intermediate  ratio.  Thus  the  expressions, 
2A-f3B  :  2A  +  5B  :  2A  +  7B  :  represent  a  scries  of  com- 
pounds, of  which  our  .future  studies  will  afford  us  several 
cases.  ^ 

187.  Equivalent  -Proportions. — This  jpayoe  considered 
as  the  most  important  law  in  chernic*tphilosoph*y,  and  its 
discovery  and  application  have  been  the  great  cause  of  the 
rapid  advance  of  modern  chemistry.  Chemical  analysis  has 
shown  that  the  body,  oxygen,  can  form  one  definite  com- 
pound, or  more  than  one,  with  every  other  clement  yet  dis- 
covered, except  perhaps  fluorine.  The  compounds  of  oxy- 
gen with  the  elements  being  perfectly  definite,  (18.3,)  can 
all  be  expressed  in  numbers,  which  numbers  will  truly  ex- 
press the  combining  weights  of  the  several  bodies.  For  the 
sake  of  illustration,  let  us  assume  that  it  requires  eight  parts 
by  weight  of  oxygen  to  unite  with  each  of  the  other  elements, 
and  that  these  eight  parts  require  various  weights  of  the 
several  elements.  We  can  then  make  a  table  which  shall 
correctly  express  these  numerical  relations. 

6  parts  of  carbon. 


Thus,  8  parts  of  oxygen  unite  with- 


1  part  of  hydrogen. 
35-41  parts  of  chlorine. 
108-12  of  silver. 


27-14  of  iron. 
101-27  of  mercury. 
16-09  of  sulphur. 

And  we  might  go  on  thus  through  the  whole  list  of  ele- 
mentary substances,  analyzing  their  several  compounds  with 
oxygen,  and  setting  down  the  combining  numbers  of  each 
in  one  table.  The  few  examples  given  above  are,  however, . 


186.  Illustrate  the  law  of  multiple  proportions.  187.  Illustrate 
the  law  of  equivalent  proportions.  What  is  said  of  oxygen  ?  What 
is  assumed  for  illustration  ?  How  do  other  bodies  stand  related  to 
oxygen  ?  How  has  this  been  determined  ? 


136  ELEMENTS  AND  THEIR  LAWS  OF  COMBINATION. 

sufficient  for  our  purpose.  Oxygen  is  selected  as  the  term 
of  comparison  for  the  other  bodies,  because  it  almost  uni- 
versally unites  with  the  several  other  elements.  The  number 
8  is  attached  to  it,  because  hydrogen,  which  is  made  the  unit 
in  our  books,  enters  into  combination  in  a  smaller  proportion 
than  any  other  body.  We  might  with  equal  propriety  make 
oxygen  unity,  when  hydrogen  would  be  expressed  by  a 
fractional  number.  But  taking  oxygen  as  fl,  all  the  other 
numbers  expressing  the  combining  weight  of  each  element 
have  been  determined  with  great  care,  by  often  repeated 
analyses.  Let  it  be  understood,  then,  that  if  any  of  the 
Ixxlies  in  the  table  should  form  compounds  with  each  other, 
the  weights  in  which  they  will  unite  will  be  in  the  exact  pro- 
portion of  the  numbers  severally  affixed  to  them.  Thus,  if 
hydrogen  unites  with  chlorine  to  form  a  new  compound, 
(hydro-chloric  acid,)  it  will  require  one  part  of  hydrogen  to 
85*41  parts  of  chlorine  to  form  such  compound.  One  pound 
of  hydrogen  will  unite  to  85*41  pounds  of  chlorine,  and  will 
form  36-41  pounds  of  the  compound.  Any  excess  or  de- 
ficiency of  either  of  the  dements  will  make  no  difference 
with  the  result,  and  the  above  law  will  in  all  cases  be  found 
strictly  true.  If  sulphur  and  mercury  unite  to  form  a  third 
body,  it  will  be  only  in  the  proportion  of  the  numbers  16-09 
and  101-J6;  and  if  sulphur  unite  with  iron,  it  will  be  as 
16-09  :  27-14. 

We  see  then    that    the    several    numbers    arc    truly    the 
equivalents  of  each  other,  as  they  are  all  the  equivalent  of 
oxygen,  and  are,  therefore,  most  appropriately  called  cquiva 
lent  proportions,  or  equivalent  numbers. 

188.  Table  of  Chemical  Equivalents. — In  the  following 
table,  the  equivalent  or  combining  numbers  of  all  the  ele- 
mentary bodies  are  given  in  accordance  with  the  latest  and 
best  authorities.  Two  columns  of  combining  proportions  are 
given;  in  the  first,  hydrogen,  and  in  the  second,  oxygen,  is 
used  as  the  unit  of  comparison.  Because  hydrogen  enters 
into  combination  with  other  bodies  in  a  smaller  weight  than 
any  other  known  element,  it  has  generally  been  used  in 
Great  Britain  and  in  this  country  as  the  basis  of  the  scale  of 


Illustrate  this  in  the  case  of  hydro-chloric  acid.  If  there  is  an 
excess  or  deficiency  of  either  element,  what  then?  What  term  is 
most  appropriate  to  express  this  ?  188.  What  does  the  table  show 
us  ?  What  is  said  of  the  hydrogen  scale,  and  why  has  it  been  used  ? 


COMBINATION   BY  WEIGHT. 


137 


equivalent  numbers.  It  was  also  believed,  and  is  still,  by 
some  good  chemists,  that  the  numbers  expressing  the  com- 
bining weights  of  all  bodies  would  be  found,  on  more  accurate 
research,  to  be  simple  multiples  of  the  unit  of  hydrogen.  If 
this  view  were  correct,  it  would  give  us  the  great  convenience 
of  avoiding  fractional  numbers.  But  the  most  rigid  experi- 
ments have  failed  to  prove  this  idea  to  be  true,  and  as  it  has 
no  necessary  foundation  in  the  nature  of  things,  we  are  not 
at  liberty  to  adopt  it.  Berzelius,  and  most  European  chemists, 
assume  oxygen  as  100;  and  the  second  column  of  figures 
in  the  table  gives  the  equivalents  according  to  this  scale. 

TABLE  OF  ELEMENTARY  SUBSTANCES,  WITH  THEIR  EQUIVALENTS  AND 
SYMBOLS. 


H=l, 

H=l, 

Sym- 

or 

Sym- 

or 

bol.* 

Oxv.=SOxy.=  100 

bol. 

Oxy.=8 

Oxy.=100 

Aluminium, 

Al 

1369i        171.17 

Manganese, 

Mn 

2767 

34589 

Antimony, 

Sb(l) 

129  04 

161290 

Mercury, 

Hg(6) 

101-26 

126,582 

Arsenic, 

A  a 

7521 

94008 

Molybdenum, 

Mo 

47-88 

598.52 

Barium, 

Ba 

6855 

Nickel, 

Ni 

2959 

36968 

Bismuth, 

Bi 

7095 

886  97 

Nitrogen, 

N 

1406 

175.75 

Boron, 

B 

1090 

136-20 

Osmium, 

Os 

99-56 

124449 

Bromine, 

Br 

7826 

97831 

Oxygen, 

O 

8- 

100 

Cadmium, 

Cd 

5.574 

69677 

Palladium, 

Pd 

5327 

66.590 

Calcium, 

Ca 

20 

2.50 

Phosphorus, 

P 

3138 

39228 

Carbon, 

C 

6 

75- 

Platinum, 

PI 

9868 

123350 

Cerium, 

Ce 

4503 

574.70 

Potassium, 

K(7) 

3919 

48992 

Chlorine, 

CI 

3541 

44265 

Rhodium, 

R 

52  11 

65139 

Chromium, 

Cr 

2814 

351-82 

.Selenium, 

Se 

3957 

494-58 

Cobalt, 

Co 

2952 

36899 

Silicon, 

Si 

22  18 

27731 

Columbium. 

Cm 

18459 

230743 

Silver, 

Ag(8) 

108-12 

135161 

Copper, 
Didymium, 

Cu(2) 
Di 

3165 

39570 

Sodium 
Strontium, 

N.,0, 

2327 

4:<-78 

29090 
54729 

Fluorine, 

F 

18-70 

233-80 

Sulphur, 

s 

1609 

201.17 

Glucinurn, 

O 

2650 

&31  26 

Tellurium, 

Te 

64.14 

80176 

Gold, 

Au(3) 

99.44 

1243 

Thorium, 

Th 

5959 

74490 

Hydrogen, 

H 

1 

1-25 

Tin, 

Sn(10) 

5882 

73.5  29 

Iodine, 

I 

12636 

157950 

Titanium, 

Ti 

2429 

30369 

Iridium, 

Ir 

9868 

123350 

Tungsten, 

W(ll) 

9464 

1183 

Iron, 

Fe(4) 

2714 

33921 

Vanadium, 

V 

6855 

85689 

Lantnnum. 

Ln 

Uranium, 

U 

60 

750- 

Lead, 

Pb(5) 

10356 

129450 

Yttrium, 

Y 

3220 

402.51 

Lithium, 

L 

643 

80  33 

Zinc, 

Zn 

3300 

41250 

Mapnesium, 

Mp 

12-67 

158-35 

Zirconium, 

Zr 

3362 

42020 

*  In  the  symbols,  the  Latin  names  of  the  elements  are  employed. 
Eleven  of  these  are  not  in  common  use,  viz  :  (1.)  Stibium,  (2.)  Cu- 
prum, (3.)  Aurum,  (4.)  Ferrum,  (5.)  Plumbum,  (6.)  Hydrargyrum, 
(7.)  Kalium,  (8.)  Argentum,  (9.)  Natrium,  (10.)  Stannum,  (11.) 
Wolframium,  (from  the  mineral,  Wolfram.)  Columbium  is  fre- 
quently represented  by  the  symbol  Ta,  from  Tantalum,  a  name  by 
which  the  European  chemists  distinguish  this  metal. 
12* 


138  CLEMENTS  AND  THEIR  LAWS  OF  COMBINATION. 

It  is  obvious  that  the  numlicrs  of  the  oxygon  scale  are  just 
twelve  and  a  half  times  as  largo  as  those  in  the  hydrogen 
scale;  consequently,  dividing  the  oxygen  equivalents  by  12*5 
will  give  the  hydrogen  numbers,  and  multiplying  the  latter 
by  the  same  sum  will  give  us  the  oxygen  numbers. 

189.  Combining  Numbers  of  Compounds. — It   has   been 
stated  that  the  equivalent  or  combining  proportion  of  a  com- 
pound body  is  always  the  sum  of  the  combining  equivalents 
of  its  elements.     Strict  experiment  has  established    this  im- 
portant law,  which  will  receive  constant  illustration  as  we  go 
on  ;  at  present,  however,  we  must  accept  it  as  truth,  and  not 
anticipate,  by  attempting    to   give  examples  which  cannot   be 
well    understood    until   we   have   become   somewhat    familiar 
with  chemical  language,  symbolic    illustration,  and    the  laws 

ofaffinitv.  • 

/ 

•J.   Combination  by    Volume. 

190.  (raseous  bodies,  whether  elementary  or  compound, 
combine  not  only  in  accordance  with  the  laws  just  explained, 
but  also  according  to  a  peculiar    law  of  their  own,  whereby 
certain   volumes    of   each    are    required.     The    volumes    in 
which    gaseous   bodies  unite,  are  either   1  to  1 ,  or  1  to  2,  or 
1  to  3,  &c.     Thus  water  is  formed  of  2  volumes  or  measures 
of  hydrogen,  and  1  volume  of  oxygen.     In  combining,  these 
three  volumes  are  condensed  into  two.      If  we  take  oxygen, 
hydrogen,  chlorine,  and  nitrogen,  in  the  proportions  by  weight 
in  which  they  combine,  or  measure  the  volumes  t^ey  occupy 
as   gases,  a  very  obvious  relation  will    be  observed   between 
them  ;  the  volume  of  oxygen  being  exactly  one  half  that  of 
each  of  the  others. 

Thus,    8  grains  of  oxygen  occupy  23-3  cubic  inches. 

1  grain  of  hydrogen,  46-7 

35-41  grains  of  chlorine,  46-2 

14-06  grains  of  nitrogen,  46-5 


'  How  is  one  scale  translated  into  the  other  ?  [Note.  If  the  learner 
can  commit  the  table  to  memory  with  the  hydrogen  equivalents  and 
symbols,  it  will  be  of  great  service  to  him  hereafter.]  189.  What 
is  said  of  combining  numbers  of  compounds?  190.  How  else  than 
by  weight  do  the  gases  combine  ?  Illustrate  this.  What  relation  is 
seen  between  the  equivalent  weights  and  volumes  of  bodies  ?  Name 
some  examples. 


COMBINATION    BY    VOLUMP. 


139 


The  same  is  true  of  compound  gases,  and  also  all  bodies 
which  can  be  raised  in  vapor,  as  sulphur,  iodine,  and 
mercury.  Solids,  which  combine  with  gases,  arc  subject  to 
the  same  law.  Sulphur  has  -j-  the  volume  of  oxygen,  and 
mercury  4  times. 

191.  We  can  state  this  truth  in  another  form.  If  we  call 
the  weight  of  a  volume  of  oxygen  1000,  then  an  equal 
volume  of  hydrogen  will  weigh  0-06*25,  and  these  numbers 
will  represent  the  relative  specific  gravity  of  the  gases.  But 
in  water,  two  volumes  of  hydrogen  unite  with  one  of  oxygen, 
and  we  must,  therefore,  double  the  above  hydrogen  number, 
2  X -0626  =  0-125.  Now  these  numbers,  1000  and  0-125, 
are  exactly  the  equivalent  numbers  on  the  oxygen  scale, 
100-  and  12-5,  or  making  hydrogen  unity,  then  we  have 
100-0-i- 12-5  =  8  ox.,  and  0-125-M2-5=1  hyd.  This  re- 
lation  between  the  specific  gravity  of  gaseous  bodies  and 
their  combining  number,  or  chemical  equivalents,  is  uni- 
versally true,  and  we  might  give  a  long  table  including  these 
relations  ;  but  the  following  examples  will  answer  : 


Gases  and  vapors. 

Specific  Gravities. 

Chemical   I 

quivalents. 
By  weight. 

Air  =1.  Hydrogen=l. 

By  volume. 

Hydrogen, 
Nitrogen, 
Oxygen, 
Chlorine, 
Iodine  vapor, 
Bromine  vapor, 
Mercury  vapor, 
Sulphur  vapor, 

0-069  1            1- 
0-972             14-03 
1-111             16- 
2-470             35-64 
8-701           126-30 
5-393             78- 
6-969           101. 
6-648  j         96-54 

100  or  1 
100  or  1 
50  or  J- 
100  or  1 
100  or  1 
100  or  1 
200  or  2 
16-66  or£ 

1- 

14-06 
8- 
35-41 
126-36 
78-26 
101-27 
16-09 

When  the  numbers  ki  the  second  column  are  the  same  as 
the  equivalents,  (or  with  only  a  fractional  difference,)  then  a 
volume  represents  an  equivalent.  The  other  numbers  are 
multiples  of  the  equivalent.  Thus,  2x8=  16,  the  number 
for  the  density  of  oxygen,  and  sulphur  16x6  =  96,  the 
density  of  sulphur  vapor. 

192.  Conclusions. — (1.)  If  we  know  the  proportions  by 
volume  in  which  two  gases  combine,  and  also  their  specific 

What  of  compound  gases  and  solids  ?  191.  State  this  truth  in  another 
form.  Is  this  relation  of  density  and  combining  numbers  general? 
Name  some  of  the  examples  in  the  table.  192.  What  conclusions 
are  drawn  from  the  previous  statements?  1st?  2d  ?  3d?  4th? 


140  ELEMENTS  AND  THEIR  LAWS  OF  COMBINATION. 

gravities,  we  can  calculate  the  composition  of  the  compound 
by  weight.  (2.)  Or  we  can  foretell  the  density  of  a  com- 
pound by  knowing  the  volumes  and  specific  gravities  of  its 
elements.  (3.)  If  we  know  the  volume  and  specific  gravity 
of  one  of  the  two  elements  of  a  compound,  and  of  the  com- 
pound itself,  we  can  then  calculate  its  composition  by  weight. 
(4.)  If  we  know  the  specific  gravity  and  composition  of  a 
compound  by  weight,  we  can  then  calculate  its  composition 
by  volume.  Many  examples  will  be  found  in  elementary 
chemistry  of  the  practical  application  of  these  rules. 

3.  Chemical  Nomenclature  and  Symbols. 

193.  Names  of  the  Elements. — Some  of  the  elementary 
bodies  have  been  known  from  the  remotest  antiquity,  and 
were  in  common  use  long  before  the  science  of  chemistry 
was  heard  of.  Thus  several  metals,  as  Copper,  (Cuprum,) 
Gold,  (Aurvm,)  Iron,  (Fcrrum,)  Mercury,  (Hydrargyrum,) 
Silver,  ( Argentum,)  IxMid,  (Plumbum,)  Tin,  (Stannum,) 
have  long  been  known  either  by  the  names  we  now  give 
them,  or  by  those  Latin  terms  of  which  our  Knglish  names 
are  translations.  No  descriptive  meaning  is  conveyed  by 
such  terms  as  these,  nor  by  such  as  Sulphur  and  Carbon. 
The  alchemists  named  the  metals  after  the  various  planets. 

Thus,  Gold  was  called  Sol,  the  Sun  ;  Silver,  Luna,  the 
Moon  ;  Iron,  Mars  ;  Lead,  Saturn  ;  Tin,  Jupiter ;  Quick- 
silver, Mercury  ;  and  Copper,  Venus.  Hence  formerly  the 
astronomical  signs  or  symbols  of  these  planets  were  em- 
ployed by  alchemists  and  mineralogists  to  represent  the 
names  of  these  metals,  and  they  are  still  in  use  in  some 
countries. 

Several  of  the  elements  have  been  named  from  some 
prominent  or  distinguishing  physical  property  of  color,  taste, 
or  smell,  which  they  possess  :  thus  Bromine  is  so  called 
from  the  Greek  word  bromos,  fetor ;  Chlorine,  from  chloros, 
green,  in  allusion  to  its  greenish  color ;  Chromium,  from 
chroma,  color,  because  it  makes  highly  colored  compounds, 
as  chrome-yellow  ;  Glucinum,  from  glukus,  sweet,  from  the 
sweet  taste  of  its  salts ;  Iodine,  from  ton,  a  violet,  and  eidos, 

193.  Whence  have  some  of  the  elements,  as  copper,  &c.,  received 
their  names  ='  What  did  the  alchemists  call  the  metals?  On  what 
other  principles  have  some  been  named  ?  Give  instances. 


CHEMICAL  NOMENCLATURE  AND  SYMBOLS.       141 

in  the  likeness  of;  and  so  for  many  others.  Another  class 
of  names  has  been  contrived  from  what  was  supposed  to  be 
the  characteristic  attribute  of  the  body  in  combination.  Thus, 
Oxygen  was  so  named  because  many  of  its  compounds  are 
acids,  from  the  Greek,  ojws,  acid,  and  gennao,  I  produce. 
Hydrogen  is  from  hudor,  water,  and  gennao,  I  produce.  We 
might  thus  go  through  the  whole  list,  but  fc  is  unnecessary, 
as  we  shall  have  again  to  give  the  etymology  of  these  words 
when  we  speak  of  each  element. 

194.  Names  of  Compounds.  —  All   chemical   compounds 
derive  their  names   from  one  or  more  of  their  constituents, 
according  to  certain  fixed   and   simple  rules,  which  we  must 
very     briefly    explain.       When    two    elements     unite,    the 
compound  is  called    binary,   from    6i?,    twice ;  thus  water, 
sulphuric  acid,  oxyd  of  silver,  and   oxyd  of  iron,  are  binary 
compounds.     Compounds  of  binary  combinations  with  each 
other,  as  of  sulphuric  acid  with   soda,  forming  sulphate  of 
soda,  or  Glauber's  salts,  (and  the  salts,  generally  so  called,) 
are  called   ternary    compounds,    (from    ter,   thrice.)     Com- 
pounds of  salts  with   each  other,  (as  in   the  case  of  alum, 
which  is  a  compound  of  sulphate  of  potash  and   sulphate  of 
alumina,)  are  named  quaternary  compounds,  from  quatuor, 
four. 

195.  All  the  compounds  of  oxygen  with  the  other  ele- 
ments  are  called  cither  oxyds  or  acids.     Thus,  water  in 
chemical   language  is  the  oxyd   of  hydrogen  ;  the  chemical 
name  of  potash  is  the  oxyd  of  potassium.     It  has  been  be- 
fore stated,  that  oxygen  forms  compounds  with  all  the  other 
elements,  (187.)     Some  of  these  compounds   have  what  we 
commonly  call   acid*   properties:   thus,  the  compounds  of 
oxygen  and  sulphur  are  called  acids,  and  not  oxyds.     Oxyds 
are  divided  into  two  classes ;  (a)  neutral  oxyds,  like  water  ; 


194.  How  are  compounds  named  ?  What  are  binary  compounds  ? 
What  ternary?  What  quaternary?  195.  What  are  the  oxygen 
compounds  called  ?  Give  instances.  How  are  oxyds  described  ? 
Notes.  What  are  acids  ?  What  alkalies  ?  What  bases  ? 


*  Acids  are  known  by  their  taste  in  some  cases,  and  by  their 
power  of  turning  the  vegetable  blues  to  red;  but  more  particularly 
by  their  power  of  uniting  with  and  saturating  alkalies  and  other 
bases. 


142  ELEMENTS  AND  THEIR  LAWS  OF  COMBINATION. 

(b)  alkaline*  oxyds  and  bases,f  like  potash,  alumina.  When 
the  same  element  unites  with  oxygen  in  more  than  one  pro- 
portion, (184,  2d,)  forming  two  or  more  oxyds,  then  they 
are  distinguished  by  the  Greek  prefix,  proto,  (protos,  first,) 
applied  to  that  body  which  has  the  least  portion  of  oxygen, 
which  is  called  the  protojcyd  ;  deuto,  (deuteros,  second,)  is 
prefixed  to  the  next  degree  of  oxidation,  giving  us  the  term 
dent  ox  yd ;  trito,  (tritos,  third,)  to  the  body  containing  still 
more  oxygen  than  the  deiitox yd.  The  oxyd  which  contains  the 
largest  dose  of  oxygen  with  which  the  body  is  known  to  unite, 
is  also  called  the  peroxyd,  from  the  Latin,  per,  which  is  a  par- 
ticle of  intensity  in  that  language.  Thus  there  are  two  oxyds 
of  hydrogen,  the  protoxyd  (water)  and  the  peroxyd  ;  there 
arc  three  oxyds  of  manganese;  (1.)  the  protoxyd,  (2.)  the 
deutoxyd,  (3.)  the  peroxyd  of  manganese.  Some  oxyds  arc 
formed  in  the  proportion  of  2  to  3,  or  once  and  a  half.  Such 
oxyds  are  distinguished  by  the  term  se&quioxyds,  from  the 
numeral  scsf/t/i,  (once  and  a  half.)  Certain  inferior  oxyds 
are  called  xuboxydx. 

190.  The  binary  compounds  of  chlorine,  and  some  other 
elements  which  resemble  oxygen  in  their  manner  of  combi- 
nation, and  in  their  relations  to  electrical  decomposition,  are 
also  distinguished  in  the  same  manner  as  oxygen.  Thus, 
with  the  other  elementary  l>odtes  : 

Chlorine  forms  Chlorids. 

Bromine     "       Rromids. 

Iodine          "       lodids. 

Fluorine     "       Fluorids. 

Oxygen      "      Oxyds. 

197.  The  binary  compounds  of  sulphur  analogous  to  the 
oxyds  are  called  sulphurets,  and  not  sulphids.  The  prefix 

Explain  the  terms  expressing  different  degrees  of  oxydation,  and 
their  use.  l.tf,  proto.  2<l,  dento.  3d,  trito.  \th,prr.  5th,  xesqni. 
G/A,  sub.  196.  How  are  the  binary  compounds  of  chlorine,  &c., 
named  ?  Give  instances. 


*  Alkalit*  are  soluble  bodies,  with  a  hot,  acrid  taste,  which  have 
the  power  of  saturating  acids,  and  of  turning  the  reddened  vegetable 
blues  to  blue  or  green. 

t  Base  is  a  term  given  to  all  oxyds  which  are  not  acids  :  it  is  a 
more  general  and  comprehensive  term  than  alkali.  In  fact,  all 
bodies,  simple  and  compound,  are  properly  divided  into  basts  and 
,  or  titctro-poxitive  and  elect ro-rtfgative  bodies. 


CHEMICAL  NOMENCLATURE  AND  SYMBOLS.  H3 

bi  (double)  is  more  commonly  used  before  the  compounds  of 
chlorine,  sulphur,  &c.,  than  deuto,  which  is  used  before  the 
oxyds.  Thus,  it  is  more  usual  to  say  bichloride  of  carbon, 
and  bisulphuret  of  iron,  than  deutochloride  of  carbon,  and 
deutosulphuret  of  iron.  When  the  name  of  the  element  to 
which  this  prefix  is  made  begins  with  a  vowel,  the  consonant 
n  is  introduced  as  making  a  more  euphonious  word ;  thus 
we  say  biniodid  of  lead,  rather  than  bi-iodid  of  lead.  Com- 
pounds of  phosphorus  and  carbon  with  electro-positive  ele- 
ments, are  distinguished  by  the  termination  uret,  like  those 
of  sulphur;  thus,  we  say  the  sulphuret  of  carbon,  carburet 
of  iron,  and  phosphuret  of  lead.  In  all  such  cases,  the 
name  of  the  element  which  most  resembles  oxygen,  (i.  e.  the 
electro-negative  element,)  is  that  which  stands  first  in  the 
name  of  these  compounds,  and  which  has  the  termination 
affixed  to  it.  Thus,  one  of  the  compounds  of  chlorine  and 
phosphorus  is  called  chlorid  of  phosphorus,  and  not  phos- 
phuret of  chlorine  ;  sulphuret  of  carbon,  and  not  carburet 
of  sulphur. 

198.  The  acid  compounds  of  oxygen  are  named  from  the 
substance  in  combination  with  'the  oxygen,  with  the  addition 
of  the  termination  ic,  the  word  acid  being  always  appended. 
Thus,  one  of  the  compounds  of  nitrogen  and  oxygen  is 
termed  nitric  acid  ;  of  chromium  and  oxygen,  chromic  acid. 

If  two  acid  compounds  of  oxygen  are  formed  with  an  ele- 
ment, the  termination  ous  is  applied  to  that  which  has  the 
least  oxygen ;  thus  we  have  sulphurous  acid,  and  sulphuric 
acid,  as  the  names  for  two  very  dissimilar  acids  of  sulphur. 

Sometimes  a  compound  has  been  discovered  containing 
less  oxygen  than  that  compound  which  has  already  received 
the  termination  ous;  then  the  term  hypo  is  prefixed,  (from 
the  Greek  hupo,  under,)  and  we  then  have  the  term  hypo- 
sulphurous  ;  or  hyposulphuric,  provided  an  intermediate 
compound  is  formed  between  the  sulphurous  and  sulphuric 
acid.  On  the  same  plan,  we  say  hyperchloric  acid,  (from 
huper,  above,)  to  distinguish  the  acid  of  chlorine  having  a 
higher  proportion  of  oxygen  than  chloric  acid,  before  named  ; 
perchloric  acid  has  the  same  meaning,  and  may  be  used 

197.  How  is  the  term  bi  used  ?  In  the  names  of  sulphur,  iodine,  &c., 
which  element  stands  first  ?  198.  How  are  the  acid  compounds  of 
oxygen  named?  Explain  the  use  of  the  terminations  "te"  and 
"ous."  How  is  hypo  used  in  this  connection,  and  how  hyper? 


14-4-  ELEMENTS  AND  TUElll  LAWS  OF  COMBINATION. 

with  equal  propriety.     All  other  analogous   acids  arc  named 
on  precisely  the  above  principles. 

199.  Sulphur  acids  and  hydrogen  acids  arc  those  w 
sulphur  and    hydrogen   take   the   place  of  oxygen.      Tlids, 
sulpharscnic-acid  is  an  acid   compound  of  arsenic  and  feul- 
phur.     Hydrochloric  acid  is  the  acid  formed  from  the  union 
of  hydrogen   and   chlorine.*     In   the  same   way,   we   have 
hydrobromic,  hydrofluoric,  and   hydriodic   acids,  as  acids  of 
bromine,  fluorine,  and  iodine. 

200.  (2.)   Ternary  compounds,  or  salts,  are  named  from 
the   acid    which    they    contain ;    the    termination   ic    being 
changed  into  ate,  and  ous  into  ite.     Thus,  the  salt   formed 
from  the  union  of  soda  and  nitric  acid  is  railed    the  nitrate 
of  soda,   and   that   formed   with   nitrons  acid   is  called   the 
nitrite  of  soda;    the   salts  of  hyponitrous   acid   are  called 
hyponitrites,  and  of  hyperchloric  acid,  hypcrchloratcs,  &c. 
The   species   is  always    indicated   by   the  oxyd  ;    thus,   the 
nitrate  of  lead  is  the  same  as  the  nitrate  of  the  oxyd  of  lead, 
and    nitrate  of  soda  is   the  same  as   nitrate  of  tlie  oxyd  of 
sodium  ;     the    word    oxyd    Ix'ing    understood,    is    generally 
omitted.     A  bisulphate  has  twice1,  and  a  sestfuisulphate  once 
and  a  half  as  much  acid  as  a  sulphate.     The  excess  of  base 
in  sul>salts  is  sometimes   expressed    by  the  Greek    prefix   di, 
twice;  thus,  the  dichromatc  of  lead   has   twice  as  much  of 
the  l>ase  lead  as  the  chroma te  of  lead. 

201.  (3.)  Quaternary  Compounds. — The  double  salts  are 
named  from  their  bases ;  thus  alum,  which  is  formed  of  sul- 
phate of  alumina  and   sulphate  of  potash,  is  called   double 
sulphate  of  alumina  and  potash.     The  chlorid  of  potassium 
and  platinum  is  another  double  salt,  formed   from  the  union 
of  a  chlorid  of  platinum  and  chlorid  of  potassium. 

202.  The  chemical   nomenclature,  when  once  understood, 
enables  us  after  a  little  use  to  form,  in  most  cases,  from  the 
mere  name  of  the  compound  substance,  a  correct  idea  of  its 


199.  Sulphur  acids  and  hydrogen  acids  arc  how  named  ?  200. 
How  are  salts  named  ?  Give  examples.  How  are  the  species  named  ? 
What  is  a  bi  and  scsqui  sulphate  ?  What  meaning  has  the  prefix  di  ? 
201.  (3.)  How  are  double  salts  named  ?  Give  examples. 


*  In  strict  uniformity  to  rule,  the  term  chlorohydric  is  correct,  but 
use  has  established  the  other.  The  same  remark  is  true  of  bromo- 
hydric,  fluohydric,  and  iodohydric  acids. 


CHEMICAL  NOMENCLATURE  AND  SYMBOLS.       145 

composition,  and  of  the  proportions  of  its  constituents.  This 
great  advantage  is  possessed  by  no  other  science,  and  cannot 
be  too  highly  estimated.  There  are  a  good  many  compounds, 
however,  that  have  been  discovered  of  late  years,  for  which 
this  nomenclature  provides  no  names.  But  we  have  certain 
written  expressions,  by  means  of  which  we  can  convey  an 
idea  of  all  chemical  compounds  with  a  mathematical  precision 
and  great  convenience. 

203.  Chemical  Symbols  of  the  Elements. — In   the  table 
of  Elementary  Bodies  (188)  the  "  symbols"  of  the  several 
elements  will  be  found  opposite  to  their  names.     The  sym- 
bols are  merely  the  first  letter  of  each  name,  or  the  first  two, 
when  more  than  one  element  begins  with  the   same  letter ; 
thus  O  stands  for  oxygen,  and  Os  for  Osmium ;  P  stands  for 
Phosphorus ;  PI  for  Platinum,  and  Pd  for  Palladium.     The 
second   letter  in  all  such  cases  is  small,  a  capital  letter  being 
uniformly  used  for  the  first.    The  Latin  names  are  invariably 
used  for  the  abbreviation,  and  for  this  reason  there  are  eleven 
symbols,  unlike  the  common   names  of  the  elements  they 
represent.  (See   note  to    188.)       Prof.    Berzelius    contrived 
the  system  of  symbols  now  in  use,  and  by  a  happy  thought 
he  made  each  symbol  represent  not  merely  the  substance  for 
which  it  stands,  but  one  equivalent  of  each  substance.     Thus 
O  stands  not  for  oxygen  in  general,  but  for  one  equivalent  of 
that  element;  or,  hydrogen  being  unity,  for  the  number  8.     O 
and  8  are  therefore  interchangeable  expressions,  while  O2, 
O3,  &c.,  represent  2x8  and   3x  8,  or  16  and  24,  according 
to  the  second  law  of  chemical  combination,  (184.) 

Compounds  are  represented  by  using  merely  the  symbols, 
and  sometimes  uniting  them  by  the  sign  of  addition,  (4--) 
Thus  water  will  be  represented  by  HO  or  II  -fO,  which 
means  one  equivalent  of  each  clement,  1  +  8  =  9,  which  is 
the  combining  number  of  water.  Protoxyd  of  lead  is  thus 
written  PbO,  or  Pb  +  O. 

204.  When  more  than  one  equivalent  of  an  element  is  in 
combination,  we  then  prefix  a  number  expressing  it,  like  an 
algebraic  co-efficient,  (as  5O,)  or  the  number  may  be  applied 


202.  What  great  advantage  has  the  chemical  nomenclature  ? 
203.  What  are  chemical  symbols  ?  Give  examples.  What  names 
are  abbreviated  ?  Whose  contrivance  are  the  symbols  ?  For  what 
does  the  symbol  stand?  Illustrate.  How  are  compounds  repre- 
sented ?  Give  examples  on  the  black-board. 
13 


146     ELEMENTS  AND  THEIR  LAWS  OF  COMBINATION. 

above  on  the  right,  (as  O\)  or  below  on  the  right,  (as  O5;) 
each  of  these  expressions  means  five  equivalents  of  oxygen. 

We  can  write  nitric  acid  N5O,  or  NO5,  or  NO3,  the  latter 
being  the  usual  mode;  sometimes,  but  not  often,  the  +  or 
comma  (,)  is  used  between  them,  as  N-f  Os,  or  N,O5. 
Such  expressions  are  called  formula;;  thus  the  formula  for 
sulphuric  acid  is  SO3,  or  S-fO3,  from  which  we  know  that 
the  combining  number  of  sulphuric  acid  is  16-f^3,  or 
16  +  24  =  40.  When  two  compounds  unite  to  form  a  new 
body,  the  sign  -f»or(,)  is  used  between  them;  thus,  sul- 
phate of  oxyd  of  iron  is  written  FcO  +  SO3,  or  FeO,SO3. 
The  small  figures  apply  only  to  the  letters  to  which  they  are 
attached  ;  larger  figures  used  before  the  compound,  apply  to 
the  whole  formula ;  thus,  3SO3  means  three  equivalents  of 
sulphuric  acid ;  but  the  sign  +  prevents  the  passage  of  this 
meaning  beyond  the  sign.  Thus  2FcO-fSOa  means  two 
equivalents  of  oxyd  of  iron  and  one  of  sulphuric  acid ;  in 
order  to  make  the  figures  apply  to  both,  we  must  write  it 
2(FcO  +  SO,,)  cir  2(FeO,SO3.) 

In  chemical  symbols,  the  oxygon,  or  element  most  nearly 
resembling  it,  (i.  c.  the  electro-negative  element,)  is  placed 
last ;  the  base  (or  electro-positive  element)  being  placed  first. 
Thus  we  say  SO3  for  dry  sulphuric  acid,  and  not  O3S.  A  com- 
pound of  sulphuric  acid  (SO3)  and  water  contains  2  equiva- 
lents of  water,  only  one  of  which  is  however  chemically 
combined  as  a  base  with  the  acid.  We  can  make  this 
apparent  to  the  reader  in  constructing  the  formula  thus, 
HO,SO3-f  IIO;  the  comma  signifies  a  closer  union  than 
the  +,  and  the  first  equivalent  of  water  is  in  intimate  union 
with  the  acid,  forming  a  sulphate  of  water,  while  the  second 
portion  is  combined  with  this  sulphate.  Compounds  which 
contain  water,  like  common  sulphuric  acid,  nitric  acid,  and 
many  mineral  bodies,  are  termed  hydrous. 

205.  The  symbols  are  sometimes  abbreviated  still  further, 
to  simplify  the  expression  of  very  complex  combinations. 
This  is  done  by  expressing  one  equivalent  of  oxygen  by  a 


204.  How  is  more  than  one  equivalent  expressed  ?  Show  the 
different  modes  in  which  nitric  acid  is  expressed  ?  How  is  the 
union  of  compounds  expressed  ?  Tell  the  difference  between  the 
small  and  large  figures.  Which  element  is  placed  first  in  symbols  ? 
Illustrate.  How  can  we  make  the  peculiar  construction  of  hydrous 
sulphuric  acid  seen  /  What  are  hydrous  bodies? 


CHEMICAL    AFFINITY.  147 

dot,  two  by  two  dots,  &o.  Thus  S  signifies  the  same  as  SO3, 
(dry  sulphuric  acid.)  Common  crystallized  alum  is  written 
in  full,  thus, 

Al  A,3S03  +  KO,S03  +  24HO. 
We  can  conveniently  condense  this  long  expression  ;  thus 

AlS3-fKS  +  24H. 

The  short  line  under  the  Al  signifies  two  equivalents  of  the 
base.  Sometimes  the  double  equivalent  of  base  is  denoted 

by  a  black  letter,  thus,  Al,  in  place  of  the  line  beneath.  In 
Berzelius's  original  symbols  the  short  line  is  made  through 
the  type  in  the  lower  half.  Sulphur  is  in  like  manner  signi- 
fied by  a  comma ;  thus,  bisulphuret  of  iron,  Fe,S2,  may  be 

more  shortly  written  Fe.  The  constant  use  of  these  sym- 
bolic expressions  in  the  elementary  chemistry  will  soon 
familiarize  the  learner  with  their  use  and  meaning.  They 
have  contributed  very  much  to  the  progress  of  the  science, 
and  arc  invaluable  as  a  ready  means  of  comparing  as  well 
as  expressing  the  composition  of  compound  bodies. 

4.  Chemical  Affinity. 

206.  We  have  already  explained  (12  and  13)  what  is 
meant  by  chemical  affinity,  as  the  power  which  unites  two 
or  more  unlike  bodies  to  form  a  third  substance,  whose 
properties  differ  from  those  of  its  constituents.  Chemical 
affinity,  or  the  capability  of  union,  is  not  possessed  alike  by 
all  bodies.  Oxygen,  as  before  stated,  is  the  only  element 
capable  of  forming  chemical  compounds  with  all  other  ele- 
ments. Carbon  can  unite  with  oxygen,  sulphur,  hydrogen, 
and  some  other  bodies,  but  no  compound  has  been  formed 
between  it  and  gold,  silver,  fluorine,  aluminium,  iodine,  bro- 
mine, &c.  It  is,  therefore,  said  to  have  no  affinity  for  these 
bodies,  or  no  capability  of  union  with  them.  The  power  of 
union  among  bodies,  or  affinity,  is  exceedingly  different  in 
degree,  and  is  much  affected  by  many  circumstances.  Thus 

205.  Illustrate  on  the  black-board  the  abbreviation  of  symbols  in 
the  case  of  alum.  How  is  sulphur  in  combination  signified  by 
symbols  ?  206.  What  is  chemical  affinity  ?  Is  it  equal  in  all 
bodies  ?  Illustrate  by  examples. 


148  ELEMENTS  AND  THEIR  LAWS  OF  COMDIXATION. 

a  body  A  may  unite  with  a  body  B,  forming  a  third  body 
AB  ;  but  if  a  body  C  had  been  present,  A  might  have  so 
much  more  affinity  for  C  than  it  has  for  B,  as  to  unite  with 
it,  forming  AC,  while  B  would  remain  unailectcd.  For 
example,  sulphuric  acid  and  soda  will  unite  to  form  Glau- 
ber's salts,  or  sulphate  of  soda ;  but  if  soda  and  baryta  had 
Ixjth  been  present,  and  sulphuric  acid  were  added,  only  the 
sulphate  of  baryta  (or  heavy  spar)  would  be  formed,  and 
the  soda  would  remain  disengaged,  unless  there  was  sulphuric 
acid  enough  to  satisfy  all  the  baryta  and  soda  too.  This  is 
what  is  sometimes  called  elective  affinity,  as  if  the  acid 
selected  the  baryta  rather  than  the  soda. 

207.  The  more  unlike,  ns  a  general  thins,  any  two  txxhes 
arc  in  chemical   properties,  the  stronger  is  their  disposition  to 
unite.     The  metals,  as  a  class,  have  very  little  disposition  to 
unite  with  each  other,  and  when  they  do  so  it  is  not  generally 
in  chemical   proportions.     But   they  do  unite   with   oxygen, 
chlorine,  sulphur,  &c.,  forming  fixed   and   determinate  com- 
(MHinds.      The   alkalies,   j)otash   and   soda,  form   no   proper 
compound  with  each  other,  and   their  alkaline   properties  arc 
not  altered   by  sucli  union.     Sulphuric  and  nitric  acid  may 
be   mingled    in   any    proportion,    but    no   new   compound   is 
formed,  and  the  mixture  is  still  acid.      But  if  the  (xjtash  and 
soda  IKJ   put  with  the   nitric   and   sulphuric   acid,  separately, 
and   in  their  combining   proportions,  the  result  will   be   two 
compound  Ixidies,  having  neither  acid  nor  alkaline  properties. 
If  the  nitric  acid  is  added  to  its  equivalent  of  potash,  we  shall 
have  saltpetre,  or  nitrate  of  potassa,  while  the  sulphuric  acid 
in  like  manner  will  unite  with  its  equivalent  of  soda,  forming 
sulphate  of  soda,  or  Glauber's  salts. 

208.  Solution  is  the  result  of  a  feeble  affinity,  but  one  in 
which   the   properties  of  the   dissolved   body  arc  unaltered  ; 
thus,  sugar  is  dissolved  in  all  proportions  in  water  or  alcohol, 
and  a  drop  of  the  solution  may  IKJ  mingled   in  an  ocean  of 
water.     Camphor  is   soluble  in   alcohol,  in  any  proportion, 
but  the  addition  of  water  to  the  solution  will   cause  the  cam- 
phor to  be  thrown  down.     Gum  is  soluble  in  water,  but  not 
in  alcohol.     We    have  already   seen,   that   the  solution  of 


What  is  meant  by  "elective  affinity"  207.  What  principal 
condition  of  affinity  is  named  ?  Illustrate  this.  208.  What  is  said 
of  solution  ? 


CHEMICAL    AFFINITY.  149 

various  salts  in  water  would  produce  cold  (111)  from  the 
change  of  state  in  the  hody  dissolved. 

200.  The  circumstances  which  modify  the  action  of 
affinity  are  numerous,  some  of  which  we  may  briefly  notice. 
We  have  said  (16)  that  chemical  affinity  existed  only  among 
unlike  particles,  and  at  insensible  distances.  Intimate  con- 
tact among  particles  is,  therefore,  in  the  highest  degree 
necessary  to  promote  chemical  union.  Any  circumstance 
which  favors  such  contact  will  increase  the  activity  of,  or 
disposition  to,  chemical  combination.  Solution  brings  par- 
ticles near  together,  and  leaves  them  free  to  move  among 
each  other ;  substances  in  a  state  of  solution  have,  therefore, 
an  opportunity  to  unite,  which  they  do  not  possess  when 
solid.  Hence  the  old  maxim,  "  Corpora  non  agunt  nisi  sint 
soluta."  Carbonate  of  soda  and  tartaric  acidj  for  example, 
both  in  a  dry  state,  will  never  unite ;  but  the  addition  of  water 
will  at  once,  by  dissolving  them,  bring  about  a  union.  Heat 
will  often  cause  union  to  take  place,  being,  in  fact,  a  most 
powerful  means  of  solution.  Sand  or  silica  will  not  unite 
with  soda  or  potash  by  contact  or  aqueous  solution,  but  if 
the  mixture  in  proper  proportions  is  strongly  heated,  union 
takes  place  and  glass  is  formed.  Sulphur  will  not  unite  with 
cold  iron,  but  if  the  iron  be  heated  to  redness,  or  the  sulphur 
melted,  a  vigorous  union  takes  place,  and  a  sulphuret  of  iron 
results. 

Cohesion  (10)  is  strongly  opposed  to  chemical  union,  or 
affinity,  and  any  means  which  will  overcome  it  will  promote 
the  union  of  the  elements.  Solution  and  heat  both  act  by 
overcoming  cohesion  ;  and  the  fine  mechanical  division  of  a 
body,  or  pulverization,  does  the  same. 

210.  Bodies  in  the  nascent*  state  (as  it  Js  called)  will 
often  unite,  when  under  ordinary  circumstances  no  affinity  is 
seen  between  them.  Thus  hydrogen  and  nitrogen  gases, 
under  ordinary  circumstances,  do  not  unite  if  mingled  in  the 
same  vessel ;  but  when  these  two  gases  are  set  free  at  the 
same  time,  from  the  decomposition  of  some  organic  matter, 

209.  What  circumstances  modify  or  are  essential  to  affinity  ?  How 
does  solution  favor  it  ?  Illustrate.  How  does  heat  favor  it  ?  Illus- 
trate. How  does  cohesion  affect  it  ?  What  counteracts  cohesion  ? 
210.  What  of  bodies  in  the  nascent  state  ?  Illustrate  this. 

*  From  nascens,  being  born,  or  in  the  moment  of  formation. 
13* 


150         I:LI:.MI:NTS  AND  THEIR  LAWS  OF  COMBINATION. 

they  readily  unite,  forming  ammonia.  The  same  is  true  of 
carbon  under  the  same  circumstances,  which  will  then  unite 
in  a  great  variety  of  proportions  with  hydrogen  and  nitrogen, 
although  no  such  union  can  l>c  ('fleeted  among  these  bodies 
separately. 

1*11.  The  quantity  of  matter,  as  well  as  the  order  and 
condition  in  which  substances  may  be  presented  to  each 
other,  often  exerts  an  important  influence  on  the  power  of 
affinity.  Thus  vapor  of  water,  when  passed  through  a  gun- 
barrel  heated  to  redness,  will  be  decomposed,  the  oxygen 
uniting  with  the  iron,  while  the  hydrogen  escapes  at  the  other 
end  of  the  tube.  On  the  contrary,  if  hydrogen  gas  is  passed 
over  oxyd  of  iron  in  a  tube  heated  to  redness,  the  oxygen  of  the 
ox  yd  unites  with  the  hydrogen,  leaving  metallic  iron,  while 
steam  (formed  from  the  union  of  the  hydrogen  with  the 
oxygen  from  the  iron)  issues  from  the  open  end  of  the  tube. 
Numerous  examples  of  this  sort  might  be  given,  where  the 
play  of  affinities  seems  to  be  determined  by  the  prcjKUidcrancc 
of  one  sort  of  matter  over  another,  or  by  the  peculiar  con- 
dition of  the  resulting  compounds,  as  regards  insolubility,  or 
the  power  of  vapori/ation. 

212.  The  presence  of  a  third  body  often  causes  a  union, 
or  the  exertion  of  the*  force  of  affinity,  when  this  third  body 
takes  no  part  in  the  changes  which  happen.  Thus,  oxygen 
and  hydrogen  gases  may  he  mingled  without  any  combination 
taking  place  between  them,  although  a  strong  affinity  exists. 
If,  however,  a  portion  of  platinum  in  a  state  of  very  fine 
division  (spongy  platinum)  be  introduced  into  the  mixture, 
union  takes  place,  sometimes  slowly,  but  more  often  with  an 
explosion,  the  platinum  being  at  the  same  time  heated  to 
redness  from  ihe  rapid  union  of  the  gases  which  takes  place 
in  its  pores.  Advantage  is  taken  of  this  fact  in  constructing 
the  common  instrument  for  lighting  tapers  by  a  stream  of 
hydrogen  falling  on  spongy  platinum.  No  change  is  suffered 
in  this  case  by  the  platinum,  which  seems  to  act  by  its 
presence  only.  Berzclius  has  proposed  the  term  catalysis, 
from  the  Greek  kata,  bv,  and  luo,  to  loosen,  to  express  the 
peculiar  power  which  some  bodies  possess  of  aiding  chemical 
changes  by  their  presence  merely.  We  shall  have  occasion 

211.  What  of  quantity  of  matter  ?  Give  an  example.  212.  What 
is  meant  by  the  influence  of  presence  ?  Illustrate  this.  What  other 
term  expresses  these  cases  ? 


ATOMIC    THEORY.  151 

to  refer  to  this  subject  again.  The  case  of  the  platinum  is 
much  more  intelligible  than  many  other  instances  of  con- 
tact-union and  decomposition  of  which  chemistry  offers  ex- 
amples, since  it  appears  to  act  by  its  power  of  condensation, 
to  bring  the  particles  within  combining  distance. 

5.  Atomic  Theory. 

213.  We  have  already  (7  and  8)  said  something  of  atoms 
as  being  the  smallest  conceivable  state  in  which  matter  exists. 
As  all   ponderable   matter  is   assumed   to   be   formed  by  an 
aggregation  of  a  series  of  these  atoms,  the  interesting  question 
at  once  arises,  do  the  chemical  equivalents  or  combining 
weights  of  the  several  elements  express  the  relative  weights 
of  their  atoms?     Dr.   Dalton   first  proposed   the  view   now 
universally  accepted,  which  assumes  this  to  be  the  fact.     All 
that  has  been  said   in   this  chapter  on  the  combining  weights 
of  bodies,  &c.,  has  been  the  result  of  rigorous  chemical  in- 
vestigation, and  is  capable  of  demonstrable  proof.     Dallon's 
hypothesis  of  the  relative  weights  of  ultimate  atoms  is  only 
theoretical,  but  has   been  found   to  conform  in  a  remarkable 
degree  to  the  results  of  experience.     We  may  feel  some  good 
degree  of  certainty  in  the  belief  that  we  know  the  actual  re- 
lation of  weight  between  the  ultimate  atoms  or  molecules  of 
the  elements.     There  is  no  doubt  that  tho  atom  of  sulphur  is 
two  times  heavier  than  that  of  oxygen  ;  but  we  know  nothing 
of  their  actual  weight. 

214.  We  can  now,  perhaps,  better  understand   why  the 
equivalent  numbers  of  bodies  should   always  be  multiples  of 
each  other.     If  the  atom  of  oxygen  be  represented  by  eight, 
(and  we  cannot  conceive  of  an  atom  as  being  divided,)   then 
any  compound  containing   more  than  one  atom  of  oxygen, 
must  have  twice,  thrice,  or  four  times  eight,  and  so  on.     On 
this  view  of  atoms,  all  the  four  great  laws  of  chemical  com- 
bination (184)  receive  a  remarkable  corroboration,  as  a  little 
reflection  will  show.     The  atomic  weight  of  a  body  is  there- 
fore as  correct  an  expression  as   its  equivalent  weight,  or 
combining  proportion.     We  might  easily  illustrate  this  theory 
to  the  senses   in  a  gross  way,   by  a  series  of  spheres    so 
marked  as  to  represent   the  several  atoms  of  elementary 

213.  What  is  the  atomic  theory?     214.  What  help  does  it  give  in 
understanding  chemical  facts  ? 


152  CRYSTALLIZATION. 

bodies,  the  union   of  which   would   show  the  compound  re- 
sulting from  the  union  of  atoms. 

6.   Specif  c  Heat  of  Atoms. 

215.  Specific  heat  has  already  been  explained,  (106.) 
If  in  place  of  comparing  equal  weights  of  different  bodies 
together,  we  take  them  in  atomic  proportions,  we  shall  find 
tin-  numbers  representing  the  sj>ecific  heat  of  lead,  tin,  zinc, 
enpper,  nickel,  iron,  platinum,  sulphur,  and  mercury,  to  l>e 
identical  ;  while  tellurium,  arsenic,  silver,  and  gold,  although 
equal  to  each  other,  will  be  twice  that  of  the  nine  previous 
Ixxlies,  and  iodine  and  phosphorus  will  be  lour  times  as 
much.  Tin;  general  conclusion  drawn  from  these  and  other 
similar  facts  is,  that  the  atoms  of  all  simple  substances  have 
the  same  capacity  for  heat.  The  specific  heat  of  a  Ixuly  would 
thus  aflord  the  means  of  fixing  its  atomic  weight.  There 
can  b<;  no  doubt  of  the  truth  of  this  in  numerous  cases,  but 
experiments  arc  still  wanting  to  show  it  to  be  universally 
true.  Compound  atoms  have  in  some  cases  been  shown  to 
have  the  same  relations  to  heat  as  the  simple.  This  is  true 
of  many  of  the  carbonates,  and  some  sulphates.  A  more 
minute  discussion  of  the  atomic  theory  would  be  out  of  place 
in  this  work. 


II.  CRYSTALLIZATION. 

1.  Nature  of  Crystallization  and  Primary  Forms  of 
Crystals. 

216.  Nature  of  Crystallization.  —  The  forms  of  living 
nature,  both  animal  and  vegetable,  are  determined  by  the 
laws  of  vitality,  and  are  generally  bounded  by  curved  lines 
and  surfaces.  Inorganic  or  lifeless  matter  is  fashioned  by  a 
different  law.  Geometrical  forms,  bounded  by  straight  lines 
and  plane  surfaces,  take  the  place  in  the  mineral  kingdom 
which  the  more  complex  results  of  the  vital  force  occupy  in 
the  animal  and  vegetable  world.  The  power  which  de- 
termines the  forms  of  inorganic  matter  is  called  crystallization. 


215.  What  relation  has  specific  heat  to  the  atomic  theory  ?  216. 
What  parallel  is  drawn  between  the  forces  of  living  and  inorganic 
nature. 


NATURE    OP    CRYSTALLIZATION.  153 

A  crystal  is  any  inorganic  solid,  bounded  by  plane  surfaces 
symmetrically  arranged,  and  possessing  a  homogeneous 
structure. 

Crystallization  is,  then,  to  the  inorganic  world,  what  the 
power  of  vitality  is  to  the  organic;  and  viewed  in  this,  its 
proper  light,  the  science  of  crystallography  rises  from  the  low 
station  of  being  only  a  branch  of  solid  geometry,  to  occupy 
an  exalted  philosophical  position.  We  sec,  therefore,  the 
importance  of  devoting  a  brief  space  to  this  subject  in  con- 
sidering the  general  principles  of  Chemical  Philosophy. 

The  cohesive  force  in  solids  (10)  is  only  an  exertion  of 
crystalline  forces,  and  in  this  sense  no  difference  can  be 
established  between  solidification  and  crystallization.  The 
forms  of  matter  resulting  from  solidification  may  not  always 
be  regular,  but  the  power  which  binds  together  the  molecules 
is  that  of  crystallization. 

217.  Circumstances  influencing  Crystallization. — Solu- 
tion is  one  of  the  most  important  conditions  necessary  to 
crystallization.  Most  salts  and  other  bodies  are  more  soluble 
in  hot  than  in  cold  water.  A  saturated  hot  solution  will 
usually  deposit  crystals  on  cooling.  Common  alum  and 
Glauber's  salts  are  examples  of  this.  Solution  by  heat  or 
fusion  also  allows  of  crystallization,  as  is  seen  in  the  crys- 
talline fracture  of  zinc  and  antimony.  Sulphur  crystallizes 
beautifully  on  cooling  from  fusion,  and  so  do  bismuth  and 
some  other  substances.  The  slags  of  iron  furnaces  and 
scoria?  of  volcanic  districts  present  numerous  examples  of 
minerals  finely  crystallized  by  fire.  The  glass,  which  cools 
slowly  after  long  fusion,  in  the  clay  fire-pots  of  our  glass- 
houses, has  often  beautiful  star-formed  opaque  white  crystals 
found  in  it,  and  the  whole  mass  of  the  glass  sometimes 
becomes  crystalline  and  opaque.  Blows  and  long  continued 
vibration  produce  a  change  of  molecular  arrangement  in 
masses  of  solid  iron  and  other  bodies,  resulting  often  in  the 
formation  of  broad  crystalline  plates.  Rail-road  axles  are 
thus  frequently  rendered  unsafe.  In  short,  any  change  which 
can  disturb  the  equilibrium  of  the  particles,  and  permits  any 
freedom  of  motion  among  them,  favors  the  re-action  of  the 
polar  or  axial  forces,  (218,)  and  promotes  crystallization. 

What  is  crystallization  said  to  be  ?  What  is  the  cohesive  force? 
217.  Name  some  circumstances  which  influence  crystallization. 


CRYSTALLIZATION. 


- 

1 

|3 

^ 

r 

V  V            y 

/ 

Magnetism  influences  and  promotes  crystallization.    When 
,    ^.,,.y  ^—         ~/z\       nitrate  of  mercury  on  a  glass  plate  is 
— \    placed  over   the  poles  of  an  electro- 
magnet, as  in  the  figure,  crystalliza- 
tion takes   place  in  the  curved  lines 
here  shown.     By  substituting  a  plate 
of  copper  for  the  glass,  it  is  curiously 
etched  in  the  magnetic  curves  by  the 
acid  of  the  silver  salt.     These  experi- 
ments  may  be  much  varied  by  the  ingenuity  of  the  learner. 
The  observations  of  Mr.  R.  Hunt  have  given  us  much  new 
information  on  this  point. 

218.  Polarity  of  Molecules. — The  laws  of  crystallization 
show  that  the  molecules  (or  ultimate  particles  of  matter)  have 
polarity.  That  is,  these  molecules  have  three  imaginary 
axes  passing  through  them,  whose  terminations,  or  poles,  are 
the  centre  of  the  attractions  (10)  by  which  a  series  of  similar 
particles  are  attracted  to  each  other  to  form  a  regular  solid. 
These  molecules  are  either  spheres  (a)  or  ellipsoids,  (r,)  and 
the  three  axes  (N.  S.)  are  always  either  the  fundamental 
axes  or  the  diameters  of  these  particles.  In  the  sphere  (a) 


these  axes  are  always  of  equal  length,  and  at  right  angles  to 
each  other,  and  the  forms  which  can  result  from  the  aggre- 
gation of  such  spherical  particles  can  be  only  symmetrical 
solids,  such  as  the  cube  and  its  allied  forms.  The  cube 
drawn  about  the  sphere  a  may  be  supposed  to  be  made  up  of 
a  great  number  of  little  spheres  (b)  whose  similar  poles 
unite  N.  and  S.  In  the  ellipsoid  (c)  all  the  axes  may  vary 
in  length,  giving  origin  to  a  vast  diversity  of  forms.  All 


What  is  said  of  the  power  of  magnetism  in  this  respect?  218. 
What  do  the  laws  of  crystallization  show  ?  What  are  the  axes  of 
molecules  ?  What  forms  have  the  molecules  of  bodies  ?  What 
forms  can  come  from  the  spherical  particles  ?  How  may  the  struc- 
ture of  the  cube  be  shown  ?  How  are  the  axes  of  the  ellipsoid  ? 


PRIMARY    FORMS    OF    CRYSTALS. 


155 


matter  not  subject  to  the  vital  force  is  endowed  with  such 
polarity  inherent  in  its  molecules.* 

219.  Crystalline  Forms. — The  mineral  kingdom  presents 
us  with  the  most  splendid  examples  of  crystals ;  yet,  in  the 
laboratory  we  can  imitate  the  productions  of  nature,  and  in 
many  cases  produce  beautiful   forms  from  the  crystallization 
of  various  salts,  which  have  never  been  observed  in  nature. 
The  learner  who  is  ignorant  of  the  simple   laws  of  crystal- 
lography, sees  in  a  cabinet  of  crystals  an   unending  variety 
and  complexity  of  form,  which  at  first  would   seem  to  baffle 
all  attempts  at  system  or  simplicity.     Numerous  as  the  natu- 
ral forms  of  crystals  are,  however,  they  may  be  all  reduced 
to  six  classes,  comprising  only  thirteen  or  fourteen   forms, 
which  are  called  the  primary  forms,  because  all  other  crys- 
talline solids,  however  complex  or  varied,  may  be  formed 
from  them  by  certain  simple  laws. 

220.  Primary  forms. —  The  first  class  of  primary  forms 
includes  the  cube,  (1,)  the  octahedron,  (2,)  and  the  dodeca- 
hedron,   (3.)     The 

faces  of  the  cube 
are  equal  squares. 
The  eight  solid  an- 
gles are  similar, 
and  also  the  twelve 
edges.  The  three  1  2  3 

axes  are  equal,  (aa,  bb,  cc,)  and  connect  the  centres  of 
opposite  faces.  The  regular  octahedron  (2)  consists  of  two 
equal  four-sided  pyramids,  placed  base  to  base.  The  six 
solid  angles  are  equal,  and  so  also  the  edges,  which,  as  in 
the  cube,  are  twelve  in  number.  The  plane  angles  are  60°, 
and  the  interfacial  109°  28'  16".  The  axes  connect  the 
opposite  angles ;  they  are  equal,  and  intersect  at  right  angles. 


To  what  matter  do  these  axial  attractions  belong  ?  219.  How 
are  the  complex  forms  of  crystals  arranged  and  simplified?  220. 
Describe  the  first  class  of  primary  forms. 


*  We  thus  see  that  atoms  or  molecules  are,  as  before  remarked, 
only  the  centres  of  several  forces,  whose  aggregate  results  we  call 
matter.  Under  the  influence  of  heat,  the  crystallogenic  attraction 
loses  its  polarity  and  force,  and  the  body  becomes  liquid  or  gaseous. 
The  return  to  a  solid  state  can  occur  again  only  when  the  attractions 
become  polar  or  axial. 


156 


CRYSTALLIZATION. 


This  class  is  also  called  the  monomctric,  (mono*,  one,  and 

metron,  measure,)  the  axes  being  equal. 

221.    The  second  class  includes  the  square  prism,  (4,)  and 

square  octahedron,  (o.)  In  the  square  prism  (-4)  the  eight 
solid  angles  are  right  angles,  and 
similar,  as  in  the  culie.  The  eight 
basal  edges  are  similar,  but  differ 
from  the  four  lateral.  The  two 
basal  laces  are  squares,  the  four 
lateral  are  parallelograms.  The 
axes  connect  the  centres  of  oppo- 
site faces,  and  intersect  at  right 
varv  in  the  length  of  the  vertical 


MM 

1- 

'cS 

s~\ 

: 

Square   prisms 


4 

angles. 

axis,  (</,  «,)  which  is  hence  called  th<-  varying  axis;  the 
lateral  axes  (bb,  cc)  are  equal.  This  class  is  also  called  the 
dimctric,  (dis,  twofold,  and  metron,  measure.) 

222.  The  third  class  contains  the  rhombic  prism,  (0,)  the 
rectangular  prism,  (7,)  and    the    rhombic   octahedron,  («.) 

The  rhombic,  prism  (6) 
has  two  sorts  of  edges, 
two  acute  and  two  ob- 
tuse. The  solid  angles 
are,  therefore,  of  two 
kinds,  four  obtuse  and 
~*  four  acute.  The  axes 

7  arc  unequal,  and  cross 

at  right  angles.  The  lateral  connect  the  centres  of  opposite 
edges,  bb,  cc.  Tin;  basal  faces  arc  rhombic.  The  rect- 
angular prism  (7)  has  all  its  solid  angles  similar.  There 
arc  three  kinds  or  sets  of  edges,  four  lateral,  four  longer 
basal,  and  four  shorter  basal.  The  axes  connect  the  centres 
of  opposite  faces,  and  intersect  at  right  angles.  The  three 
arc  unequal.  The  rhombic  octahedron  ($)  lias  three  unequal 
axes,  connecting  opposite  solid  angles.  All  the  sections  in 
this  solid  are  rhombic.  This  class  is  also  called  the  trirnetric, 
from  tris,  threefold,  and  inctron,  measure.  * 

223.  The  fourth  class  contains  the  oblique  rhombic  prism, 
(0,)   and   the   riirht    rhomboidal   prism,   (10.)     The   oblique 
rhombic  prism  is  represented  in  the  figure  as  inclining  away 


221.  What  are  the  forms  of  the  second  class?  Describe  them. 
222.  What  forms  make  up  the  third  class?  Describe  them.  223. 
What  forms  docs  the  fourth  da  ;s  contain  ?  How  do  they  differ  t 


PRIMARY  FORMS  OF  CRYSTALS. 


157 


from  the  observer,  the  prism  being  in  position  when  standing 
on  its  rhombic  base.  The  upper  and 
lower  solid  angles  in  front  are  dis- 
similar, one  obtuse  and  the  other 
acute.  The  four  lateral  solid  angles 
are  similar.  Two  of  the  lateral 
edges  are  acute,  and  two  obtuse ;  and 
the  same  is  true  of  the  basal.  The 


10 


lateral  axes  are  unequal ;  they  connect  the  centres  of  oppo- 
site lateral  edges,  and  intersect  at  right  angles.  The  vertical 
axis  is  oblique  to  one  lateral  axis,  and  perpendicular  to  the 
other.  The  right  rhomboidal  prism  (10)  has  two  obtuse 
and  two  acute  lateral  edges,  and  four  longer  and  four  shorter 
basal  edges.  The  solid  angles  are  of  two  kinds,  four  obtuse 
and  four  acute.  The  axes  connect  the  centres  of  opposite 
faces;  one  is  oblique,  the  others  cross  at  right  angles. 
This  is  also  called  the  monoclinate,  (monos,  one,  and  cli?w, 
to  incline,)  having  one  inclined  axis. 

224.  The  fifth   class  includes   the  oblique  rhomboidal 
prism.     In  this  solid  only  those  parts  diagonally 

opposite  are  similar,  and  consequently  it  has  six 
kinds  of  edges.  The  axes  connect  the  centres 
of  opposite  faces.  They  are  unequal,  and  all 
their  intersections  are  oblique.  This  is  called 
the  triclinate  class,  from  tris,  three,  and  clino, 
to  incline,  the  three  axis  all  being  obliquely  in- 
clined. 

225.  The  sixth  class  includes  the  hexagonal  prism,  (12,) 
and    the    rhombohedron, 

(13  and  14.)  The  hex- 
agonal prism  has  twelve 
similar  angles,  and  the 
same  number  of  similar 
basal  edges.  The  lateral 
edges  are  six  in  number, 
and  similar.  The  lateral 
axes  arc  equal,  and  cross  at  60°,  connecting  the  centres  of 
opposite  lateral  faces  or  lateral  edges. 


12 


IS 


What   other  names   have  the    first,  second,  and   third   classes  ? 
221.  What  solid  is  included  in  the  fifth  class?     225.  Name  the  two 
solids  in  the  sixth  class  of  primary  forms.     How  are  the  hexagonal 
prism  and  rhombohedron  related  ? 
14 


158  CRYSTALLIZATION. 

The  rhombohedron  is  a  solid  whose  six  faces  arc  all 
rhombs.  The  two  diagonally  opposite  solid  angles  (a  a) 
consist  of  three  equal  obtuse  or  equal  acute  plane  angles,  and 
the  diagonal  connecting  these  solid  angles  is  called  the  verti- 
cal axis,  (a  a.)  When  the  plane  angles  forming  the  vertical 
solid  angles  are  obtuse,  the  rhombohedron  is  called  an  obtuse, 
(l.'i,)  and  if  acute,  it  is  called  an  acute  rhoml>ohedron,  (14.) 
The  three  lateral  axes  arc  equal,  and  intersect  at  angles  of 
00°  ;  they  connect  the  centres  of  opposite  lateral  edges. 
This  will  be  seen  on  placing  a  rhombohedron  in  position  and 
looking  down  upon  it  from  above.  The  six  lateral  edges  will 
be  found  to  be  arranged  around  the  vertical  axis,  hke  the 
sides  of  a  hexagonal  prism. 

220.  The  mutual  relations  of  the  primary  forms  are  well 
shown  in  the  foregoing  arrangement.  Thus,  in  each  of  the 
six  classes,  the  first  named  solid  alone  is,  pro|>erly  considered, 
a  primary  form,  the  others  in  each  class  being  frequently 
found  as  secondaries  to  these.  The  six  fundamental  forms 
are  the  cube,  square  prism,  right  rectangular  prism,  oblique 
rhombic  prism,  or  right  rhornboidal  prism,  oblique  rhomboi- 
<lal  prism,  and  the  hexagonal  prism,  or  rhombohedron. 

2.   Clear  age. 

227.  Common  isinglass,  or  mica,  will  split  into  thin  leaves 
or  plates,  which  can  be  subdivided  as  long  as  our  compara- 
tively clumsy  instruments  will  allow.  This  property  depends 
on  the  crystalline  structure  of  the  mineral,  and  is  called  its 
cleavage.  Many  other  minerals  possess  the  same  property. 
Thus,  galena  (sulphuret  of  lead)  can  be  broken  only  into 
cubes,  or  in  directions  parallel  to  one  or  more  of  the  faces  of 
a  cube.  It  differs  from  mica  in  having  three  cleavage  di- 
rections, at  right  angles  to  each  other.  Fluor-spar,  which  is 
often  found  in  culx?s,  can,  by  cleavage  of  the  solid  angles,  be 
made  into  regular  octahedrons.  Calc-spar  also  admits  of  easy 
cleavage  in  three  directions,  but  yields  only  rhombohedrons. 

Cleavage  is  not  effected  with  equal  ease  in  all  minerals : 
in  mica,  this  is  produced  by  the  finger-nail  ;  in  others,  a 
* 

How  arc  rhombohedrons  distinguished  1  226.  What  is  said  of  the 
relations  of  primary  forms  ?  What  six  fundamental  forms  are  named  1 
*J27.  What  is  cleavage  in  minerals  1  On  what  does  it  depend  ?  Give 
examples.  Is  it  equal  in  all  minerals  / 


MEASUREMENT    OF    CRYSTALS. 


159 


slight  blow  in  the  direction  of  the  cleavage  is  required,  and 
some  practice  and  skill  are  necessary  to  ensure  success. — 
Quartz  and  several  other  minerals  cleave  only  when  heated 
and  thrown  into  water ;  other  minerals  do  not  cleave  at  all. 
Cleavage,  when  attainable,  takes  place  parallel  to  some  or  all 
of  the  faces  of  the  primary  form.  It  is  obtained  with  equal 
ease  or  difficulty  parallel  to  similar  primary  faces,  and  with 
unequal  ease  or  difficulty  parallel  to  dissimilar  primary  faces  ; 
and  cleavage  parallel  to  similar  planes  aflbrds  planes  of 
similar  lustre  and  appearance,  and  the  converse. 

3.  Measurement  of  Crystals. 

228.  Common  Goniometer.* — The  angles  of  crystals  are 
measured  by  means  of  instruments  called  goniometers.     The 
common     goniome- 

ter,  which  is  here 
figured,  consists  of 
a  light  semicircle 
of  brass,  accurately 
graduated  into  de- 
grees, and  having  a 
pair  of  steel  arms 
moving  on  a  central 
pivot,  and  so  arrang- 
ed as  to  slip  in  a 
groove  over  each  other.  The  points  a  a  can  thus  be  made  to 
embrace  the  faces  of  a  crystal  whose  angle  we  wish  to  measure. 
When  the  edges  of  the  sliding  arms  exactly  fit  the  two  faces 
containing  the  required  angle,  the  screw  which  holds  them 
together  is  tightened,  and  the  graduated  semicircle  is  applied 
with  its  centre  at  the  point  of  intersection,  when  the  angle  is 
directly  read  on  the  arc,  or  its  supplement  is  given  in  the 
alternate  angles.  By  this  instrument  angles  can  be  measured 
with  only  tolerable  accuracy ;  but  where  the  greatest  nicety 
is  required,  a  much  more  delicate  instrument  is  used. 

229.  Wollaston's  Reflective  Goniometer. — The  principle 

What  is  the  law  of  cleavage  ?  228.  What  is  a  goniometer  ?  Ex- 
plain the  common  one  and  its  use.  229.  Explain  the  principles  of 
Wollaston's  goniometer  from  the  diagram. 

*  From  the  Greek,  gonia,  an  angle,  and  metron,  measure. 


160 


CRYSTALLIZATION. 


of  this  instrument  may  be  understood  by  reference  to  the 
/  d  annexed   figure,  which  represents 

/  *J*     a  crystal  (°)  whose  angle  (a  b  c)  is 

J>»^^         /  .s          required.     The  eye  at  P,  looking 

^\^/       /  at  the  face  (b  c)  of  the  crystal, 

^HJMV  observes  a  reflected  image  of  M, 

/Si  in  the  direction  P  N.     The  crys- 

^/ Mmam  tal  may  now  be  so  turned  that  the 

N        *  same  image  is  seen  reflected  in  the 

next  face,  (b  a,)  and  in  the  same  direction,  (P  N.)  To  effect 
this,  the  crystal  must  be  turned  until  a  b  has  the  present 
position  of  b  c.  The  angle  d  b  c  measures,  therefore,  the 
number  of  degrees  through  which  the  crystal  must  be  turned. 
But  d  b  c  subtracted  from  180°  equals  the  required  angle  of 
the  crystal  a  b  c  ;  consequently,  the  crystal  passes  through 
a  number  of  degrees,  which,  subtracted  from  180°,  gives  the 
required  angle.  When  the  crystal  is  attached  to  a  graduated 
circle,  which  should  move  with  it,  we  have  the  goniometer 

of  Wollaston.  In  the  annexed 
figure,  a  is  such  a  circle  of 
4>rass,  graduated  to  half  de- 
grees, and  hung  by  the  axis 
6,  on  which  it  moves  with 

d  fl  IHINLy^  Krcat  steadiness.  This  axis 
is  perforated  from  end  to  end 
for  the  passage  of  a  closely 
fitting  rod  or  central  axis,  on 
one  end  of  which  is  the  bent 
joint,  (rf,)  carrying  the  crys- 
tal, (f.)  By  the  head  c,  and 
the  arrangement  at  d,  the 
crystal  is  adjusted  without  moving  the  graduated  wheel ;  and 
when  this  is  accomplished  in  such  a  manner  that  the  eye  of 
the  observer  placed  over  the  crystal,  as  at  P,  can  see  a  clear 
image  of  a  line  on  the  wall,  (M,)  or  a  window-bar,  in  each 
face  successively,  then  the  graduated  wheel  (which  stands 
when  at  rest  at  zero  of  the  vernier  e)  is  made  to  revolve,  and 
with  it  the  crystal,  until  the  mark  or  window-bar  is  distinctly 
seen  in  the  second  face.  The  number  of  degrees  and  parts 
of  a  degree  which  correspond  to  the  angle  required,  are  thus 
obtained  directly  by  the  movement  of  the  wheel,  which  was 


How  is  this  principle  used  in  Wollaston's  instrument  ? 


ISOMORPHISM.  161 

beforehand  placed  with  180°  opposite  to  the  zero  on  the 
vernier.  The  movement  of  the  wheel  is,  therefore,  in  fact,  a 
subtraction  of  the  angle  d  b  c  from  180°.  The  great  advan- 
tage of  this  instrument  is,  that  we  can  by  its  aid  obtain  very 
precise  results,  and  often  on  crystals  too  small  to  be  held  in 
the  fingers  and  applied  to  a  common  goniometer.  A  small 
'magnifier  is  sometimes  attached  to  the  instrument,  to  render 
it  more  complete. 

230.  In  measurements  by  the  goniometer,  a  knowledge  of 
the  following  simple  principle  in  mathematics  will   be  found 
of  great  value.     "  The  sum  of  the  three  angles  of  a  triangle 
equals  180°,"  or  "  The  sum  of  the  angles  of  a  polygon  equals 
twice  as  many  right  angles  as  the  polygon  has  sides  less 
two"     If  the  figure  has  six  sides,  then  it  contains  2x  (6  — 2) 
=  8  right  angles,  or  8  X  90=720°.* 

4.  Isomorphism.^ 

231.  Identity  of  crystalline  form  was  formerly  supposed 
to  indicate  an  identity  of  chemical  composition.     We  now 
know  that  certain  substances  may  replace  each  other  in  the 
constitution  of  compounds,  without  changing  their  crystalline 
form.     This  property  is  called  isomorphism,  and  those  bases 
which  admit  of  mutual  substitution  are  termed  isomorphous. 
Chemistry  furnishes  us  many  examples  of  these  isomorphous 
bodies.     Thus   alumina  and   peroxyd  of  iron   replace  each 
other  indefinitely.     The  carbonate  of  iron  and  carbonates  of 
lime  and  magnesia  are  also  examples,  as  the  common  sparry 
iron,  (spathic  iron,)  which  is  a  carbonate  of  iron,  in  which 
a  large  portion  of  carbonate  of  lime  sometimes  crystallizes, 
without  producing  any  change  of  form  in  the  mineral.    Oxyd 
of  zinc  and  of  magnesia,  oxyd  of  copper  and  protoxyd  of  iron, 
also  take  the  place  each  of  the  other  in  compounds,  without 
any  alteration  of  crystalline  form.     When  those  bodies  unite 

230.  State  the  principles  in  this  section  regarding  triangles  and 
polygons.  Give  an  example.  231.  What  is  isomorphism  ?  Name 
some  examples. 

*  The  subject  of  crystallography  cannot  be  further  illustrated 
here ;  but  the  learner  who  desires  to  pursue  it  is  referred  to  the 
highly  philosophical  treatise  on  Mineralogy  by  Mr.  J.  D.  Dana, 
from  which  we  derive  the  substance  of  the  foregoing. 

f  Isos,  equal,  and  morpke,  form. 

u* 


162  CRYSTALLIZATION. 

with  acids  to  form  salts,  the  resulting  compounds  have  the 
same  crystalline  form,  and  if  they  have  the  same  color,  are 
not  to  be  distinguished  from  each  other  by  the  eye. 

In  double  salts,  like  common  alum,  these  relations  arc 
also  found.  The  sulphate  of  iron  may  take  the  place  of 
sulphate  of  alumina  in  common  alum,  and  -no  change  of 
form  will  occur;  and  soda  may,  in  like  manner,  replace  the 
potash.  In  fact,  all  the  similar  compounds  of  isomorphous 
bodies  have  a  great  resemblance  to  each  other,  in  general 
appearance  and  chemical  properties.  The  two  bases  in  a 
double  salt  are,  however,  never  taken  from  the  same  group 
of  isomorphous  bodies. 

232.  A  knowledge  of  this  law  is  of  great  importance  to  the 
chemist,  and  often  enables  him  to  explain,  in  a  satisfactory 
manner,  apparent  contradictions  and  anomalies,  and  to  decide 
many  doubtful  points.  It  is  supposed  that  the  elements 
whose  compounds  are  isomorphous,  arc  also  so  themselves. 
M.  Scheerer  has  noticed  the  curious  and  important  fact, 
that  in  compounds  containing  magnesia,  protoxyd  of  iron, 
and  other  bases  of  the  6th  family  below,  a  part  of  the  base 
may  be  wanting  without  a  change  of  crystalline  form,  pro- 
vided that  this  be  replaced  by  a  quantity  of  water  which  con- 
tains three  times  as  much  oxygen  as  this  part  of  the  base. 
For  example,  the  compounds — 

Mg'Si,  Mg*Si  +  311  and  MgSi  +  6H, 

in  accordance  with  this  principle,  are  isomorphous.  Thus, 
chrysolite  and  serpentine  may  be  isomorphous,  and  much  light 
is  shed  on  the  relations  of  hydrous  and  anhydrous  minerals. 
A  more  full  discussion  of  this  subject  does  not  belong  to 
our  restricted  limits,  and  we  can  only  mention,  in  conclusion, 
the  group  of  isomorphous  bodies  named  by  Prof.  Graham  in 
his  "  Elements."  1st  Family ;  Chlorine,  Iodine,  Bromine, 
Fluorine.  2d  Family ;  Sulphur,  Selenium,  Tellurium.  3d 
Family;  Phosphorus,  Arsenic,  Antimony.  4th  Family; 
Barium,  Strontium,  Lead.  5th  Family ;  Silver,  Sodium, 
Potassium,  Ammonium.  6th  Family ;  Magnesium,  Manga- 
nese, Iron,  Cobalt,  Nickel,  Zinc,  Copper,  Cadmium,  Alumi- 
nium, Chromium,  Calcium,  Hydrogen. 


What  of  salts  of  isomorphous  bases  ?     Is  it  found  in  double  salts  ? 
232.  What  six  families  of  isomorphous  bodies  are  named? 


ELECTRO-CHEMICAL   DECOMPOSITION. 


163 


233.  Dimorphism.*—  Some  substances  have  two  forms, 
under  both  of  which  they  are  found.     Thus  common  calc- 
spar  (carbonate  of  lime)  generally  occurs  in  rhombohedrons, 
(224,  13,)  but  in  arragonite  (which  is  only  pure  carbonate 
of  lime)  it  is  seen  as  a  rhombic  prism,  (221,  fig  6.) 

III.  CHEMICAL  EFFECTS  OF  VOLTAIC  ELECTRICITY. 
1.  Electro-  Chemical  Decomposition. 

234.  In  discussing  the  electricity  of  chemical  action,  (158,) 
allusion  was  made  to  the  power  possessed   by  this  species  of 
electricity  to   produce  or  modify    chemical    decomposition. 
Having  now  become  somewhat  familiar  with  the  elementary 
constitution  of  matter,  and  the  laws  of  chemical  combination, 
we  can  the  more  intelligently  proceed  to  a  very  brief  review 
of  the  chemical  effects  of  voltaic  electricity. 

235.  Decomposition  of  Water.  —  Water  was  the  first  sub- 
stance on  which  the  decomposing  power  of  the  battery  was 
observed,  soon  after  the  discoveries  of  Galvani  and   Volta 
were  made  known  in  England.     When  two  gold  or  platinum 
wires  are  connected  with  the  opposite  ends  of  the  battery,  and 
held  a  short  distance  asunder  in  a  cup  of  water,  a  train  of 
gas-bubbles  will  be  seen  rising  from  each,  and  escaping  from 
the  surface  of  the  water.     With  an  arrange- 

ment of  two  glass  tubes  placed  over  the  plati- 

num poles,  as  figured  in  the  margin,  we  can 

collect  these  bubbles  as  they  rise,  and  shall 

soon  find  that  the  gas  given  off  from  the  — 

plate  is  twice  the  volume  of  that  obtained  from 

the  -f  plate.     When  the  tubes  are  of  the  same 

size,  this  difference  of  volume  becomes  at  once 

evident   to    the   eye.      By    examining    these 

gases,  (as  will  be  explained  in  the  elementary  ~~ 

chemistry,)  we  shall   find  them,  respectively, 

pure  hydrogen  and  pure  oxygen,  in  the  exact 

proportion  of  two  volumes  of  the  former  to  one  of  the  latter, 

(190.)     By  no  modification  of  the  arrangement  can  we  cause 

233.  What  is  dimorphism  ?  234.  Why  is  electro-chemical  de- 
composition treated  in  this  place  ?  235.  Mention  the  facts  occurring 
in  the  decomposition  of  water.  How  is  this  made  more  striking  ? 
In  what  proportion  do  the  gases  rise  ?  Can  we  change  this  pro- 
portion ? 


*  From  disy  two,  and  morphe,  form. 


164  CHEMICAL  EFFECTS  OF  VOLTAIC  ELECTRICITY. 

this  process  to  vary ;  the  hydrogen  invariably  appears  on 
the  —  side,  and  oxygen  on  the  -f-  side. 

Water,  then,  is  not  only  decomposed  by  the  voltaic  current, 
but  that  decomposition  takes  place  in  the  proportions  (185) 
of  the  equivalents  of  the  elements,  and  these  elements  seek 
opposite  poles  of  the  battery. 

•j:J6.  The  experimental  researches  in  electricity  by  Mr. 
Faraday,  have  shed  much  light  on  this  subject;  and  his 
virws  being  now  generally  adopted,  it  will  be  unnecessary 
for  us  to  discuss  the  opinions  formerly  advanced  by  Volta, 
Davy,  and  others,  which  are  very  interesting  and  important 
in  the  history  of  the  science,  but  do  not  now  form  part  of  its 
first  principles.  Mr.  Faraday's  researches  required  the  intro- 
duction of  certain  new  terms,  some  of  which  we  will  now 
explain,  as  we  shall  find  them  more  convenient  than  any 
others.  (1.)  The  terminal  wires  or  conductors  of  a  battery 
are  often  termed  the  poles,  as  if  they  possessed  some  attractive 
power  by  which  they  draw  bodies  to  themselves,  as  a  magnet 
attracts  iron.  Mr.  Faraday  has  shown  that  this  notion  is  a 
mistake,  and  that  the  terminal  wires  act  merely  as  a  path  or 
door  to  the  currents,  and  he  therefore  calls  them  electrodes, 
from  electron  and  odos,  a  way.  The  electrodes  are  any 
surfaces  which  convey  an  electric  current  into  and  out  of  a 
decomposable  liquid.  The  term  electrolyses,  from  electron, 
and  the  Greek  verb  luo,  to  unloose,  is  used  to  express  decom- 
position ;  and  the  substances  suffering  decomposition  are 
termed  electrolytes.  Thus,  the  experiment  mentioned  in  the 
last  section  is  a  case  of  electrolysis,  in  which  water  is  the 
electrolyte.  The  elements  of  an  electrolyte  are  called  ions, 
from  the  Greek  participle  ion,  going,  since  the  elements  go 
to  the  -f  or  —  electrode.  The  electrodes  arc  distinguished 
ns  the  anode  and  the  cathode,  from  ana,  upwards,  and  odos, 
way,  or  the  way  in  which  the  sun  rises;  and  kala,  down- 
wards, and  odos,  or  the  way  in  which  the  sun  sets  ;  the  anode 
is  -f ,  and  the  cathode  — .  We  will  now  briefly  consider  the 

*J37.  Conditions  of  Electro-Chemical  Decomposition. — 
(1.)  All  compounds  are  not  electrolytes,  that  is,  they  are  not 
directly  decomposable  by  the  voltaic  current.  Many  bodies, 

What  do  we  infer  ?  230.  What  is  said  of  Faraday's  researches  ? 
What  did  they  require  ?  What  does  he  call  the  poles,  and  why? 
Explain  the  terms  electrode,  electrolysis,  and  electrolyte.  What 
are  ions?  237.  Are  all  compounds  electrolytes? 


ELECTROCHEMICAL    DECOMPOSITION.  165 

however,  not  themselves  electrolytes,  are  decomposed  by  a 
secondary  action.  Thus,  nitric  acid  is  decomposed  in  the 
electrical  circuit  by  the  secondary  action  of  the  nascent  (210) 
hydrogen,  which,  uniting  with  one  equivalent  of  the  oxygen, 
again  forms  water  and  nitrous  acid.  Sulphuric  acid  is  not 
an  electrolyte,  while  hydrochloric  acid  is  ;  and  the  nascent 
chlorine  from  the  latter  attacks  the  -f  electrode,  if  it  be  of  gold. 
(2.)  Electrolysis  cannot  happen  unless  the  fluid  be  a  con- 
ductor of  electricity ;  and  no  solid  body,  however  good  a 
conductor,  has  ever  been  thus  decomposed.  A  plate  of  ice, 
however  thin,  interposed  between  the  electrodes,  will  entirely 
prevent  the  passage  of  the  power ;  but  the  electrolysis  will 
proceed  as  soon  as  the  least  hole  melts  in  the  ice,  through 
which  the  power  can  pass.  Fluidity  is  therefore  a  very 
essential  condition  of  electrolysis.  The  fluidity  may  be  that 
of  heat,  or  of  solution;  thus,  the  chlorids  of  lead,  silver,  and 
tin,  are  not  electrolysed  in  a  solid  state,  but  when  fused  they 
are  decomposed  with  ease.  (3.)  The  ease  of  electro-chemi- 
cal decomposition  seems  in  a  good  degree  proportioned  to  the 
conducting  power  of  the  fluid.  Thus,  pure  water  is  by  no 
means  a  good  conductor,  and  its  electrolysis  is  difficult ;  but 
the  addition  to  it  of  a  few  drops  of  sulphuric  acid,  or  of 
some  other  soluble  conductor,  greatly  promotes  the  ease  with 
which  it  is  decomposed.  (4.)  The  amount  of  electrolysis  is 
directly  proportioned  to  the  quantity  of  electricity  which 
passes  the  electrodes.  (5.)  The  binary  compounds  of  the 
elements,  (194,)  as  a  class,  are  the  best  electrolytes.  Water 
and  iodid  of  potassium  are  instances ;  while  sulphuric  acid, 
which  has  three  equivalents  of  base  to  one  of  acid,  is  not  an 
electrolyte.  No  two  elements  seem  capable  of  forming  more 
than  one  electrolyte.  (6.)  Most  of  the  salts  are  resolvable 
into  acid  and  base.  Thus,  sulphate  of  soda  is  resolved  into 
sulphuric  acid,  which  appears  at  the  -f  electrode,  and  will 
there  redden  a  vegetable  blue ;  and  the  soda  which  appears 
at  the  —  electrode  will  restore  the  previously  reddened  blue ; 
so  that  by  reversing  the  direction  of  the  current,  these  striking 
effects  are  also  reversed. 


Give  examples.  What  is  the  second  condition  of  electrolysis  ? 
Give  examples.  (3.)  To  what  is  the  ease  of  electrolysis  pro- 
portioned ?  (4.)  To  what  is  its  amount  owing  ?  (5.)  What  class 
of  compounds  are  the  best  electrolytes  ?  Give  examples.  (6.)  What 
of  salts  ?  Give  examples. 


166  CHEMICAL  EFFECTS  OF  VOLTAIC  ELECTRICITY. 

233.  (7.)  A  single  ton,  as  bromine,  for  instance,  has  no 
disposition  to  pass  to  cither  of  the  electrodes,  and  the  current 
has  no  effect  upon  it.  There  can  be  no  electrolysis  except 
when  a  separation  of  ions  takes  place,  and  the  separated 
elements  go  one  to  each  electrode.  (8.)  There  is  no  such 
thing,  in  fact,  (as  has  been  often  supposed,)  as  an  actual 
transfer  of  ions  from  one  part  of  the  fluid  to  either  electrode. 
In  the  case  of  water,  for  example,  (235,)  oxygen  is  given  out 
on  one  side  and  hydrogen  on  the  other.  In  order  that  tin's 
may  be  the  case,  there  must  be  water  between  the  electrodes. 
We  cannot  believe  that  the  separation  of  the  elements  takes 
place  at  the  electrode  where  one  clement  is  evolved,  and  that 
the  other  travels  over  unseen  to  the  opposite  electrode. 

\Vc  may,  however,  conceive  of 
water  in  its  quiet  state,  as  repre- 
sented by  the  annexed  diagram, 
1®1®I®J®1®]®)®'  each     molecule     being    firmly 

united     by    polar    attractions 

(21 S)  to  every  other,  and  that  the  electrolytic  force  of  the 
electric  current  lias  power  to  disturb  this  polar  equilibrium, 
each  molecule  being  similarly  atlected.  In  this  case  the 
electrolysis  will  proceed  from  particle  to  particle  through  the 
whole  chain  of  affinities,  decomposing  and  recomposing,  unti4 
the  ultimate  particle  on  each  sidr,  having  no  polar  force  to 

neutralize  it,  escapes  at 
that  electrode  which  has  a 
polarity  opposite  to  itself. 
This  explanation  may  be 
better  understood,  perhaps, 
by  inspecting  the  second  diagram,  which  represents  a  series 
of  compound  molecules  of  water  undergoing  electrolysis,  the 
H  and  O  being  eliminated  at  the  opposite  extremities.  The 
same  explanation  will  be  found  to  serve  for  all  other  cases  of 
electrolysis,  both  simple  and  secondary. 

1239.  (9.)  A  surface  of  water,  and  even  of  air,  has  been 
shown  capable  of  acting  as  an  electrode,  proving  that  the 
contact  of  a  metallic  conductor  with  the  decomposing  fluid  is 
not  essential.  The  discharge  from  a  powerful  electrical 

238.  (7.)  What  is  said  of  a  single  ion?  (8.)  What  of  the  transfer 
of  ions  ?  Give  the  explanation  offered  of  the  decomposition  of  water. 
239.  (9.)  What  is  said  of  electrolysis  without  metallic  con- 
ductors ?  Explain  the  experiment  of  the  electrolysis  of  sulphate  of 
Boda  by  the  electrical  machine. 


ELECTRO-CHEMICAL   DECOMPOSITION.  167 

machine  (153)  was  made  to  pass  from  a  sharp  point  through 
air  to  a  pointed  piece  of  litmus  paper  moistened  with  sulphate 
of  soda,  and  then  to  a  second  piece  of  turmeric  paper  simi- 
larly moistened.  This  discharge  had  power  to  effect  a  true 
electrolysis ;  the  blue  litmus  was  reddened  by  the  sulphuric  acid 
set  free  from  the  sulphate  of  soda,  while  the  yellow  turmeric 
was  turned  brown  by  the  alkaline  soda  from  the  same  salt. 

240.  (10.)  Electrolysis  takts  place  in  a  series  of  com- 
pounds in  the  precise  order  of  their  equivalents.     I'hus  if 
wine-glasses  are  arranged  in  a  series,  and  in  one  is  placed 
sulphate  of  soda,   in  another  acidulated  water,   in   another 
iodid  of  potassium,  and  in  another  hydrochloric  acid,  and  if 
the  whole  series  be  connected  together  by  siphon  tubes,  or 
moistened    lampwick,  passing    from   glass   to  glass,   and  a 
powerful    galvanic   current   be  then    passed   through  them, 
electrolysis  will  occur  in  all,  but  not  in  an  equal  degree. 

It  has  been  proved  by  accurate  experiment,  that  the  decom- 
position which  ensues  is  in  exact  proportion  to  the  equivalents 
of  each  substance.  In  other  words,  we  may  say  it  requires 
one  equivalent  of  electricity  to  decompose  one  equivalent  of 
an  electrolyte,  formed  from  the  union  of  an  equivalent  of  acid 
and  another  of  base.  Conversely,  from  the  fact  that  an 
equivalent  of  electricity  is  required  to  decompose  any  com- 
pound, it  is  proved  that  the  opposite  elements  of  this  compound, 
in  uniting,  will  disengage  the  same  equivalent  of  electricity. 

241.  (11.)  The  passage  of  a  current  within  the  cells  of  a 
voltaic  battery  (2G2)  depends  also  upon  the  decomposition  in 
each  cell,  equally  with  that  between  the  platinum  electrodes. 
The  same  phenomena  which  we  notice  in  the  decomposing 
cell  (235)  take  place  also  in  each   battery  cell.     Water  is 
decomposed,  and  the  hydrogen  is  given  off  from  the  positive 
plate,  while  the  oxygen  combines  with  the  zinc,  and  thus 
escapes  detection.     Therefore,  no  fluid  not  an  electrolyte  is 
suitable  to  excite  a  battery.     Acid  water  acts,  for  this  purpose, 
only  by  the  decomposition  of  the  water,  and  oxydation  of 
the  zinc.     The  presence  of  the  acid  is  useful  only  so  far  as 
it  combines  with  the  oxyd  of  zinc  constantly  accumulating  on 

240.  How  does  electrolysis  occur  in  a  series  of  compounds  ?  In 
other  words,  what  do  we  say  ?  Conversely,  what  ?  241.  How  does 
a  current  pass  in  the  cells  of  a  battery  ?  What  happens  in  each  cell  ? 
What  is  requisite  in  the  fluid  used  to  excite  a  battery  ?  How  does 
acid  water  act  in  the  battery  ? 


168 


CHEMICAL  EFFECTS  OF  VOLTAIC  ELECTRICITY. 


'9 ,       us, 

=Jm  ""-• 

\W  'U«*y 


• 


(he  zinc  plate,  which  must   be  removed  as  fast  as  formed,  in 
order  to  keep  up  a  steady  flow  of  electricity. 

2.  From  what  has  been  said,  we  can  see  that  a  decom- 
posing cell  interjKwsed 
in  the  circuit  will  give 
us  an  exact  account  of 
amount  of  electri- 
city flowing.  Such  an 
instrument  has  been 
called  by  Faraday  a 
voltameter,  (measurer 
of  voltaic  electricity,) 
and  is  figured  in  the 
margin,  (a.)  It  differs 
from  the  decom|K>sing 
cell,  (235,)  in  being  a 

single  cell,  and  having  a  ground  glass  tube  at 
top  bent  twice,  «o  as  to  deliver  the  accumu- 
lating  gases  into  a   graduated    air-vessel,  in 
which    their  volume    is   measured.      A  more 
simple   form  of  the  apparatus  is  easily  con- 
st ructed,  as  shown  in  6,  which  is  a  short  piece 
of  glass  tube,  with   two  corks  and  a  bent   tube,  (t.)      Tho 
elect nxJc's  /*  p  pass   through  the  corks, 
arid  should  terminate  in  broad  plates  of 
platinum   foil.     A  common   form  of  the 
instrument  is  seen  in  the  annexed  figure, 
which   has  only  one   tube,  and   that   is 
graduated.      When  this  is  filled  with  the 
mixed    gases,    and    a    lighten!   match   is 
applied  to  the  open  end,  the  two  elements 
unite  again,  with  a  loud  explosion   and 
vivid     flash.       If    the   apparatus    is   so 
arranged    that    this    can    be  done  over 
water   without    access  of  air,   the   fluid 
rushes  up  to  fill  the  vacuum  occasioned 
by  the  re-union  of  the  elements   in  the 
formation  of  water. 

243.   The  theories  which   have  been 
proj)oscd  to  account  for  electro-chemical 


242.  What  is  a  voltameter  ?     What   does   it   show  ?     Explain  the 
figures.     When  the  mixed  gases  are  fired,  what  happens  ? 


SUSTAINING    BATTERIES.  169 

decomposition  and  the  action  of  the  voltaic  circuit,  we  cannot 
discuss  here,  any  further  than  to  say  that  the  chemical 
theory  first  proposed  by  Dr.  Wollastun  is  now  generally 
accepted.  Volta  argued  that  the  contact  of  different  metals 
was  essential  to  the  production  of  a  current.  The  researches 
of  Faraday,  however,  in  confirming  the  chemical  view  of 
Wollaston,  have  completely  disproved  the  contact  theory.  A 
very  simple  experiment  by  Faraday  illustrates  this  statement. 
A  slip  of  amalgamated  sheet  zinc  bent  at  a  right  angle  is  hung 
in  a  glass  of  dilute  acid  ;  on  it  is  laid  a  folded  piece  ,-- — 
of  bibulous  paper  moistened  with  iodid  of  jxrtas- 
sium.  A  platinum  plate,  with  an  attached  wire 
of  the  same  metal,  is  now  placed  in  the  acid 
water,  but  not  in  contact  with  the  zinc ;  the 
sharpened  end  of  the  wire  is  bent,  so  as  to  touch 
the  moistened  paper,  and  very  soon  it  is  discolored 
by  a  brown  spot  made  by  the  free  iodine,  liberated 
from  the  electro-chemical  decomposition  of  the 
iodid  of  potassium,  with  which  the  paper  is 
moistened.  There  is  no  contact  of  metals,  and  the  current 
is  excited  only  from  the  decomposition  of  the  iodid  out  of  the 
cell,  and  of  the  water  in  it.  A  very  strong  argument  in 
favor  of  the  chemical  theory  has  been  before  mentioned,  (161,) 
that  the  direction  of  the  current  is  always  determined  by  the 
nature  of  the  chemical  action — the  metals  most  acted  on 
being  always  positive.  Professor  Herzelius,  in  view  of  the 
facts  of  electricity,  considers  all  chemical  action  as  the  result 
of  opposite  electrical  states  in  the  elements  and  their  compounds. 
We  have  now  made  all  the  explanations  that  are  necessary 
to  enable  us  to  understand  the  principles  and  construction  of — 

2.  Sustaining  Batteries. 

Vi44.  Local  action. — In  the  old  forms  of  batteries  made 
of  copper  and  zinc  unamalgamatcd,  (164,)  there  is  always 
a  great  amount  of  local  action  in  each  cell,  arising  from  the 
impurity  of  the  zinc.  We  have  before  explained  how,  by 
amalgamating  the  zinc  with  mercury,  it  is  reduced  to  a  state 
of  electrical  uniformity,  (161,  note.)  In  order  to  have  a 
constant  voltaic  current  of  equal  power,  not  only  the  evils 


243.  What  two  theories  have  been  proposed  to  account  for  the 
electrical   phenomena   of  electrolysis  ?      What  simple  experiment 
disproves  the  contact  theory  ?     244.  What  are  sustaining  batteries? 
15 


170 


CHEMICAL  EFFECTS  OF  VOLTAIC  ELECTRICITY. 


arising  from  local  action  must  be  avoided,  but  also,  in  some 
degree,  the  weakening  of  the  acid  solution.  Batteries  so  con- 
structed as  to  meet  these  difficulties,  are  called  sustaining 
batteries,  or  constant  batteries.  We  will  first  mention 

DaniclPs  Constant  Battery.  —  This  truly  philo- 
sophical instrument  (a  vertical  section  of 
which  is  annexed)  is  made  up  of  an  ex- 
+  terior  circular  cell  of  copper,  (-f,)  three 
and  a  half  inches  in  diameter,  which  serves 
both  as  a  containing  vessel  and  as  a  nega- 
tive element ;  a  porous  cylindrical  cup  of 
earthen-ware,  (1%  fig.  6,)  (or  the  membrane 
of  an  ox-gullet,)  is  placed  within  the  copper 
cell,  and  a  solid  cylinder  of  amalgamated 
zinc  ( —  7.)  within  the  porous  cup.  The 
outer  cell  (c)  is  charged  by  a  mixture  of 
eight  parts  of  water  and  one  of  oil  of 
vitriol,  saturated  with  blue  vitriol,  (sulphate 
of  copper.)  £omc  of  the  solid  sulphate  is 
also  suspended  on  a  perforated  shelf,  or  in 
a  gauze  bag,  to  keep  up  the  saturation, 
is  filled  with  the  same  acid  water,  but  without 
Any  number  of  cells  so  arranged  arc  easily 


The;  inner 

the  copper  salt. 


(/>)  connected  together  by  binding  screws,  as  in  the 
.  figure — the  c  of  one  pair  to  the  z  of  the  next, 
9  and  so  on.  This  instrument,  when  arranged 
and  charged  as  here  descrilK-d,  will  give  out  no 
gas.  The  hydrogen  from  the  decomposed  water 
is  not  given  otF  in  bubbles  on  the  copper  side,  as 
in  all  forms  of  the  simple  circuit  of  zinc  and 
copper;  because  the  sulphate  of  copper  there 
present  is  decomposed  by  the  circuit,  atom  for 
atom,  with  the  decomposed  water,  and  the 
hydrogen  takes  the  atom  of  o.xyd  of  copper, 
appropriating  its  oxygen  to  form  water  again, 
and  metallic  copper  is  deposited  on  the  outer  cell. 
No  action  of  any  sort  results  in  this  battery, 
when  properly  arranged,  until  the  poles  are 
joined.  Ten  or  twelve  such  cells  form  the  most  active, 
constant,  and  least  costly  battery  which  can  be  procured. 

245.  Explain  PanirlFs  Battery  from  the  fignre.  What  is  its 
principle  of  action  /  What  becomes  of  the  hydrogen  7  When  does 
this  batterv  act  ? 


SUSTAINING    BATTERIES.  171 

246.  Grove's  Battery. — Professor  Grove,  of  London,  has 
contrived  another  compound  sustaining  battery,  of  great  power, 
and  most  remarkable  intensity  of  action.     The 

metals  used  are  platinum  and  amalgamated  zinc.  _  \ 
A  vertical  section  of  this  battery  is  shown  in  the  "N 
annexed  figure.  The  platinum  (  -f- )  is  placed  in 
a  porous  cell  of  earthenware,  containing  strong 
nitric  acid.  This  is  surrounded  by  the  amalga- 
mated zinc  (  —  )  in  an  outer  vessel  of  dilute  sul- 
phuric acid,  (six  to  ten  parts  water  to  one  of 
acid,  by  measure.)  The  platinum,  being  the 
most  costly  metal,  is  here  surrounded  by  the 
zinc,  in  order  to  economize  its  surface  as  much 
as  possible.  In  this  battery  the  hydrogen  of  the 
decomposed  water  on  the  zinc  side  enters  the  nitric  acid  cell, 
decomposes  an  equivalent  of  the  acid,  forming  water  with 
one  equivalent  of  its  oxygen,  while  the  deutoxyd  of  nitrogen 
is  given  out  as  a  gas,  and  coming  in  contact  with  the  air  is 
converted  into  nitrous  acid  fumes.  No  other  form  of  battery 
can  be  compared  with  this  for  intensity  of  action.  A  series 
of  four  cells  (the  platinum  foil  being  only  three  inches  long 
and  half  an  inch  wide)  will  decompose  water  with  great 
rapidity ;  and  twenty  such  cells  will  evolve  a  very  splendid 
arch  of  light  from  points  of  prepared  charcoal,  and  deflagrate 
all  the  metals  very  powerfully.  It  is  rather  costly,  and 
troublesome  to  manage,  as  are  all  batteries  with  double  cells 
and  porous  cups.  The  author  has  contrived  a  very  efficient 
form  of  the  same  battery,  in  which  mineral  carbon  (plumbago) 
is  substituted  for  the  platinum  ;*  and  the  carbon  battery  of 
Bunsen  is  constructed  on  the  same  principles,  and  produces 
most  brilliant  effects.  But  all  other  batteries  yield  in  sim- 
plicity and  ease  of  management  to  that  contrived  by  Mr. 
Smee. 

247.  Smee's  Battery  is   formed  of  zinc  and  silver,  and 
needs  but  one  cell  and  one  fluid   to  excite  it.     The  silver 
plate  (S)  is  prepared  by  coating  its  surface  with  platinum, 
thrown  down  on  it  by  a  voltaic  current,  in  the   state  of  fine 


246.  What  is  Grove's  Battery  ?  How  does  it  differ  from  the  last  ? 
How  does  it  act?  What  is  its  energy?  247.  What  is  Smee's 
Battery? 

*  American  Journal  of  Science,  (1st  series,)  vol.  xliii,  p.  393. 


172  CHEMICAL  EFFECTS  OF  VOLTAIC  ELECTRICITY. 

division,  which  is  known  as  platinum-black.  The  object  of 
this  is  to  prevent  the  adhesion  of  the  liberated  hydrogen  to 
the  polished  silver.  Any  polished  smooth  surface  of  metal 
will  hold  bubbles  of  gas  with  great  obstinacy,  thus  preventing 
in  a  measure  the  contact  between  the  fluid 
and  the  plate  by  the  interposition  of  a  film 
of  air-bubbles.  The  roughened  surface 
produced  from  the  deposit  of  platinum- 
black  entirely  prevents  this.  The  zinc 
plates  (z  z)  in  this  battery  arc  well  amal- 
gamated, and  face  both  sides  of  the  silver. 
The  three  plates  are  held  in  position  by  a 
clamp  at  top,  (&,)  and  the  interposition  of 
a  bar  of  dry  wood  (w)  prevents  the  passage 
of  a  current  from  plate  to  plate.  Water, 
acidulated  with  one-seventh  its  bulk  of  oil 
of  vitriol,  or,  for  less  activity,  with  one- 
sixteenth,  is  the  exciting  fluid.  The  quantity  of  electricity 
excited  in  this  battery  is  very  great,  but  the  intensity  is  not 
as  great  as  in  those  compound  batteries  just  described,  where 
there  is  a  double  electrolysis,  and  of  course  a  double  intensity 
acquired.  This  battery  is  perfectly  constant,  does  not  act 
until  the  poles  are  joined,  and,  without  any  attention,  will 
maintain  a  uniform  flow  of  power  for  days  together.  A  plate 
of  lead,  well  silvered,  and  then  coated  with  platinum-black, 
will  answer  equally  as  well,  and  indeed  better  than  a  thin  plate 
of  pure  silver.  This  battery  is  recommended  over  every 


other   for   the   student,  as   comprising   the   great  requisites 
of  cheapness,   ease    of   management,   and    constancy.      A 

How  is  the  silver  plate  prepared  ?  What  is  the  use  of  the  pla- 
tinum-black ?  How  is  this  battery  excited  ?  What  acts  as  well  a.9 
silver  ?  What  recommends  this  batterv  over  others  ? 


ELECTRO-METALLURGY.  173 

form  of  it,  well  calculated  for  the  student's  laboratory,  is  here 
shown,  which  is  a  porcelain  trough  with  many  cells.  This 
battery  is  the  one  universally  employed  in  electro-metallurgy. 

3.  Electro-metallurgy. 

248.  The  depositing  of  metals  by  electrical  agency 
seems  to  have  been  suggested  by  Daniell's  battery.  It  has 
been  remarked,  that  the  copper  of  the  sulphate  of  copper  in 
the  outer  cell  of  that  battery  is  deposited  in  a  metallic  state. 
The  procuring  of  a  pure  metal  in  a  perfectly  malleable  state, 
by  means  of  a  current  of  electricity,  is  a  most  important 
fact,  and  has  given  rise  to  a  new  and  valuable  art,  which  is 
every  day  extending  its  applications.  We  thus  accomplish, 
in  fact,  a  cold  casting  of  copper,  silver,  gold,  zinc,  and  many 
other  metals ;  and  a  new  field  of  great  extent  has  been  thus 
opened  for  the  application  of  metallurgic 
processes.  The  very  simple  apparatus  re- 
quired to  show  these  results  experimentally, 
is  represented  in  the  annexed  figure.  It  is 
nothing,  in  fact,  but  a  single  cell  of  Daniell's 
battery.  A  glass  tumbler,  (S,)  a  common 
lamp-chimney,  (P,)  with  a  bladder-skin  tied 
over  the  lower  end  and  filled  with  dilute 
acid,  is  all  the  apparatus  required.  A  strong 
solution  of  sulphate  of  copper  is  put  in  the 
tumbler,  (S,)  and  a  zinc  rod  (Z)  in  P ;  the 
moulds,  or  casts,  (?n,  m,)  are  seen  suspended 
by  wires  attached  to  the  binding  screw  of  Z.  Thus  arranged, 
the  copper  solution  is  slowly  decomposed,  and  the  metal  is 
evenly  and  firmly  deposited  on  wz,  m.  A  perfect  reverse 
copy  of  m  is  thus  obtained  in  solid  malleable  copper.  The 
back  of  m  is  protected  by  varnish,  to  prevent  the  adhesion 
of  the  metallic  copper  to  it.  In  this  manner  the  most  elabo- 
rate and  costly  medals  are  easily  multiplied,  and  in  the  most 
accurate  manner.  In  practice,  casts  are  made  in  fusible 
metal  of  the  object  to  be  copied,  and  the  operation  is  con- 
ducted in  a  separate  cell,  containing  only  the  sulphate  of 
copper,  one  of  Smee's  batteries  supplying  the  power.  The 

248.  What  first  suggested  electro-metallurgy  ?  What  is  required 
in  order  to  obtain  several  metals  in  the  metallic  state  ?  Explain 
the  process  for  obtaining  the  copy  of  a  medal. 

15* 


174  CHEMICAL  EFFECTS  OF  VOLTAIC  ELECTRICITY. 

art  is  also  now  extensively  applied  to  plating  in  gold  and 
silver  from  their  solutions ;  the  metals  thus  deposited 
adhering  perfectly  to  the  metallic  surface  on  which  they  are 
deposited,  provided  these  be  quite  clean  and  bright.  Many 
details  in  these  processes,  very  needful  to  the  successful 
practice  of  the  art,  are  necessarily  omitted  here.  The  reader 
is  referred  for  further  information  to  Mr.  Smee's  excellent 
"  Elements  of  Electro-Metallurgy,"  or  Walker's  "  Electro- 
type Manipulation,"  re-published  at  Philadelphia. 

249.  We  have  now  finished  our  preliminary  view  of  those 
great  powers  of  nature,  whose  operations  we  see  to  a  greater 
or  less  extent  in  every  chemical  process.  It  may  be  thought 
that  we  have  devoted  too  large  a  space  to  the  topics  already 
discussed  ;  but  the  author  is  convinced,  from  long  observation, 
that  if  the  principles  of  chemical  philosophy  are  well 
acquired  by  the  student,  but  little  difficulty  will  be  experienced 
in  afterwards  pursuing,  even  alone,  and  without  the  aid  of  a 
teacher,  the  wide  detail  of  elementary  chemistry.  In  entering 
on  the  execution  of  the  remaining  portion  of  our  task,  it  is 
with  the  full  understanding  that  no  attempt  is  made  on  our 
part  at  presenting  even  a  complete  outline  of  the  countless 
facts  of  elementary  chemistry.  Only  such  selections  will  be 
made  from  them  as  are  deemed  most  in  point  to  illustrate  and 
enforce  the  principles  already  laid  down,  and  to  increase  our 
familiarity  with  the  philosophy  of  chemistry.  It  is  hoped 
that  this  course  will  be  satisfactory  to  both  teacher  and  pupil, 
and  the  apology  implied  in  this  remark  is  intended  to  explain 
any  apparent  deficiencies  which  may  be  seen  on  the  suc- 
ceeding pages.  The  complete  and  philosophical  treatises 
of  Turner,  Kane,  and  Graham,  are  all  excellent  works  of 
reference  for  the  more  advanced  student. 

249,  What  is  said  of  the  importance  of  chemical  philosophy? 


PART  III.— INORGANIC  CHEMISTRY. 

CLASSIFICATION  OF  ELEMENTS. 

250.  A  natural  order  and  perspicuous  classification  is  of 
the  greatest  service  to  the  student  in  any  department  of 
science.  We  will  not  discuss  the  various  modes  which  have 
been  adopted  in  chemistry  for  arranging  the  elementary 
bodies  and  their  compounds,  since  such  discussions  can  have 
but  little  value  while  we  are  unacquainted  with  the  characters 
and  affinities  of  the  bodies  which  we  propose  to  classify. 
It  is  usual  to  divide  elementary  bodies  into  two  great  groups, 
the  non-metallic  and  metallic  elements.  This  convenient 
arrangement  is  founded  on  characters  which  in  a  general  and 
popular  sense  are  correct  and  easily  distinguished,  but  which 
fail  in  several  cases  to  afford  any  accurate  distinction.  No 
one  can  doubt  to  which  classes,  for  example,  gold  and  sulphur 
should  be  respectively  referred ;  but  it  is  impossible  to  say 
why  carbon  and  silicon  are  not  as  well  entitled  to  be  classed 
in  the  same  group  with  the  metals  as  tellurium  and  arsenic, 
if  we  except  the  single  character  of  lustre.  While  there- 
fore we  retain  these  general  divisions,  we  should  not  hesitate 
to  depart  from  them  whenever  by  so  doing  we  can  present 
the  facts  of  elementary  chemistry  in  a  clearer  and  more  im- 
pressive manner. 

We  will  discuss  the  first  division  of  elementary  bodies  in 
the  following  order : — 

C  i      The    only    element   \yhich   forms   com- 

CLASS  i.    <  1.  Oxygen.  V  pounds  with  all   others,  and  the  type  of 
(  }  electro-negative  bodies. 

1      Four  elements  very  similar  in  all  their 
2.  Chlorine,        sensible  properties,  and  forming  similar 


CLASS  n. 


3.  Bromine,      [compounds  with  the  metals,  and  whose 

4.  Iodine,          [acid   compounds   with  oxygen,  are   also 

5.  Fluorine.        similar,  and    have    the   constitution  ex- 

J  pressed  by  RO,  R04,  RO5,  RO7.* 


250.  What  is  the  value  of  classification  in  science  ?  What  is 
necessary  in  order  to  understand  a  classification  ?  How  are  the  ele- 
ments usually  divided  ?  What  is  said  of  this  division  ?  What  exam 
pies  are  quoted  in  illustration  ?  Give  the  classification  in  the  text. 
Name  the  bodies  in  the  second  class.  Why  are  they  associated  ? 

*  R  signifies  an  atom  of  either  of  the  electro-positive  bodies. 


176 


INORGANIC    CHEMISTRY. 


6.  Sulphur, 

CLASS  in.  4  7.  Selenium, 
8.  Tellurium. 


CLASS  iv. 


CLASS  v. 


CLASS  vi. 


9.  Nitrogen, 
10.  Phosphorus. 


These  stand  in  close  relation  with  the 
preceding,  while  their  compounds  with 
the  metals  are  more  similar  to  the  oxyds 
of  those  metals  than  are  the  analogous 
compounds  of  the  second  class.  The  oxy- 
gen acids  have  the  formula  ROj,  ROa. 

This  group  properly  includes  also 
arsenic  and  antimony,  which  are,  how- 
ever, from  convenience,  discussed  else- 
>•  where.  The  four  form  similar  com- 
pounds with  oxygen,  RO,  R03,  RO5, 
and  peculiar  gaseous  compounds  with 
hydrogen,  RHa. 

r    ,        1      These  three  bodies  are  similar,  non-vola- 
11.  car  ion,  I  ^  combustible  baseS)  and  aiike  in  form. 

}*'  Jmcon>   fing  feeble  acids  with  oxygen,  having  the 
'    J  formula  RO3. 

1  This   highly  electro-positive  body  is 
14    H  d  lunlike  any  of  the  preceding,  and  has 

r  analogies  with  the  succeeding  group 
(^  J  of  metals. 

251.  We  will  consider  these  several  classes  separately. 
The  compounds  which  each  element  forms  with  those  before 
it,  will  be  taken  up  in  order ;  and  we  shall  then  be  better  able 
to  understand  the  relation  of  each  element  to  its  associates 
in   the  same   group.     The  several   classes,  too,  will   then 
be  better  understood  in  the  analogies  which  unite,  and  the 
differences  which  separate  them. 

CLASS  I. 

1.    OXYGEN. 

Equivalent,  8.  Symbol,  O.  Density,  1*105. 

252.  History  and  Importance.  —  This  gaseous  element 
was  first  discovered  by   Dr.  Priestly,  in   1774,   and  in  the 
following  year  by  M.  Schcele,  a  Swedish   chemist.     Before 
this  discovery,  all  gaseous  bodies  were  considered  as  modifi- 
cations of  common  air,  and  oxygen  was  called  vital  air, 

What  bodies  form  the  third  class?  What  other  two  bodies 
properly  belong  in  the  fourth  class  ?  How  are  these  all  related  ? 
What  of  their  hydrogen  compounds  ?  What  bodies  are  associated 
in  the  fifth  class  ?  What  element  stands  alone  in  the  seventh  class  ? 
What  are  its  affinities  ?  251.  How  will  they  be  discussed  ?  252. 
When  and  by  whom  was  oxygen  discovered  ? 


OXYGEN. 


177 


dephlogisticated  air,  &c.  But  Lavoisier  proposed  the  name  of 
oxygen,(hom  oxus,acid9)  as  bethought  it  the  parenfrofall  acids. 
This  is  the  most  interesting  and  important  of-  the  elements. 
It  forms  more  than  one-fifth  part  of  the  atmosphere,  and 
eight-ninths  of  the  waters  of  the  globe  by  weight,  and  consti- 
tutes at  least  one-third  part  of  the  crust  of  the  planet.  By 
its  means  combustion  and  life  are  sustained,  and  it  has  the 
widest  range  of  affinities  of  all  known  substances. 

253.  Preparation. — This  gas  may  be  obtained  pure  from 
many  substances  which*  contain  it ;  but  it  is  most  easily  and 
economically  prepared  by  the  decomposition,  by  heat,  of  the 
salt  called  chlorate  of  potash.  Chloric  acid  contains  five 
equivalents  of  oxygen,  and  the  composition  of  the  salt  which 
it  forms  with  potash  is  ClOj,  KO*.  By  heat,  all  the  oxygen, 
both  in  acid  and  base,  (six  equivalents,)  is  given  off,  and 
we  have  left  KC1,  or  the  dry  chlorid  of  potassium.  The 
arrangement  of  apparatus  for  this  purpose  is  shown-  in  the 
annexed  figure.  One- 
tenth  part  by  weight 
of  pure  oxyd  of  man- 
ganese is  mingled  with 
a  convenient  portion 
of  chlorate  of  potash 
in  a  small  glass  flask, 
(a,)  to  which  a  bent 
glass  tube  is  fitted  by 
a  cork.  This  tube 
conveys  the  gas  to  the 
open  mouth  of  the  in- 
verted air-jar,  which  is 
filled  with  water.  The  heat  of  the  lamp  beneath  decom- 
poses the  salt,  and  pure  oxygen  gas  is  freely  given  off,  which 
escapes  through  the  tube  and  displaces  the  water  from  the 
air-jar.  By  aid  of  the  oxyd  of  manganese,  the  chlorate  is 


What  is  said  of  its  abundance  and  importance  ?  In  what  pro- 
portion does  it  exist  in  air,  water,  and  the  earth  ?  253.  How  do  we 
obtain  pure  oxygen  ?  Explain  the  use  of  manganese  with  the  chlo- 
rate. Why  is  the  chlorate  of  potash  able  to  yield  so  much  oxygen  ? 

*  One  ounce  of  chlorate  of  potash  will  yield  543  cubic  inches  of 
pure  oxygen  gas,  of  more  than  \\  gallons.  The  constituents  are 
in  equivalent  proportion,  Chlorine  35-41,  Potassium  39-19,  and 
Oxygen  48. 


178  NON-MET  ALL  1C    ELEMENTS. 

quietly  decomposed,  and  the  gas  comes  over  gradually;  while 
without  it  the  operation  proceeds  with  almost  explosive 
energy,  the  whole  gas  being  given  off  at  nearly  the  same 
instant.  The  glass  flask  (a)  is  protected  from  fusion  by  the 
thin  metallic  cup  (c),  in  which  is  some  dry  sand. 

254.  Oxygen   is  often   made   also   from   the   peroxyd  of 
manganese,   heated  strongly  in  a  gun-barrel  or  iron   bottle, 
from  which  a  tube  conveys   the  gas  to  the  water-trough,  or 
gas-holder.     The  gas   from   this  source   is  not  quite    pure, 
having  usually  a  little  carbonic  acicHvith  it.     One  pound  of 
peroxyd   of  manganese  will   yield  about  seven   gallons  of 
oxygen  gas,  and   the  process  is  recommended  by  its  cheap- 
ness.     Oxygen    gas  is  alsa  conveniently   obtained   by   the 
action  of  sulphuric  acid  on   the  peroxyd  of  manganese,  in 
which  case  an  apparatus  similar  to  that  above  figured   is 
employed.      Many  other  substances    yield  oxygen,   as  the 
oxyds  of  lead  and   mercury,  or  the  nitrates  of  potash  and 
soda,  when  heated  alone  in  a  suitable  vessel.     Bichromate  of 
potash  with   sulphuric  acid   may  also  be  employed   for  the 
same  purpose. 

255.  Properties  and  Experiments. — Oxygen,  when  pure, 
is  a  transparent,  colorless  gas,  which  no  degree  of  cold  or 
pressure  has  ever  reduced  to  a   liquid  state.     It  is  a  little 
heavier  than  the  atmosphere,  its  density  being,  compared  to 
air,  as  1-1057  : 1-000.     One  hundred  cubic  inches  of  the  dry 
gas  (32  and  49)  weigh  34-29   grains.     Its  most  remarkable 

O  property  is  the  energy  with  which  it  supports  com- 
bustion. Any  body  which  will  burn  in  common  air, 
burns  with  greatly  increased  splendor  in  oxygen  gas. 
A  newly  extinguished  candle  or  taper,  which  has  the 
least  fire  on  the  wick,  will  instantly  be  rekindled  in 
oxygen,  and  burn  in  it  with  great  beauty.  A  quart  of 
this  gas  in  a  narrow-mouthed  bottle,  will  easily  relight 
a  candle  fifty  times.  A  bit  of  charcoal  bark  with  the 
least  spark  of  ignition  on  it,  attached  to  a  wire  and 
lowered  into  a  jar  of  this  gas,  will  burn  with  intense 
brilliancy  as  long  as  any  of  the  gas  remains.  A  steel 
watch-spring  tipped  with  a  piece  of  burning  match,  and 
lowered  into  a  jar  of  pure  oxygen  gas,  bursts  into  the  most 


254.  How  is  oxygen  made  from  manganese  ?  What  is  the  yield  ? 
What  other  modes  are  mentioned  ?  255.  Describe  the  properties 
of  oxygen.  Explain  the  combustion  of  the  watch-spring. 


OXYGEN.  179 

magnificent  combustion ;  the  oxyd  of  iron  which  is  formed 
falls  down  in  burning  globules,  like 
glowing  meteors,  which  fuse  them- 
selves into  the  glazed  surface  of  an 
earthen  plate,  (as  in  the  figure,) 
although  covered  with  an  inch  of 
water.  If,  as  often  happens,  a 
motion  of  the  spring  throws  a  glo- 
bule of  this  fused  oxyd  against  the 
side  of  the  glass  vessel,  it  melts 
itself  into  the  substance  of  the  glass, 
or  if  that  is  thin,  goes  through  it. 
This  is  one  of  the  most  brilliant  and 
instructive  experiments  in  chemistry. 
If  the  orifice  at  top  is  closed  air-tight,  and  water  is  poured 
into  the  plate  from  a  pitcher,  we  shall  find,  as  the  experiment 
proceeds,  that  the  water  will  rise  in  the  jar  as  the  gas  is 
consumed ;  and  if  we  could  collect  and  weigh  the  globules  of 
oxyd  of  iron,  we  should  f;nd  in  them  an  increase  of  weight 
equal  to  the  weight  of  the  oxygen  consumed. 

256.  It  affects   life  when   breathed,  by  quickening  the 
circulation  of  the   blood,  and  causing  an  excitement,  which 
soon   results  in  general   inflammatory  symptoms  and  death. 
In  an  atmosphere  of  pure  oxygen  we  should  live  too  fast.     It 
exerts,  however,  no  specific  poisonous  influence,  being,  when 
used  in  moderation,  altogether  salutary,  and  often  resorted  to, 
to  inflate  the  lungs  of  drowned  persons,  and  not  unfrequently 
with  the   most  beneficial   results.     The   blood  is  constantly 
brought  into  contact  with   the  air  in   the  lungs,  and  it  is  the 
oxygen  in  the  air  which  is  the  active  agent  in  rendering  it  fit 
to  sustain  life.    As  this  is  the  first  gaseous  body  we  have  had 
occasion  to  mention,  we  will  make  a  few  remarks  on  the 

Management  of  Gases. 

257.  Pneumatic  Troughs. — Gases  not  absorbed  by  water, 
are  always  collected  in  a  vessel  of  water  called  a  pneumatic 
trough  ;  the  figure  in  253  shows  a  small  neat  one  made  of 
glass ;  but  for  practical  purposes  they  are  usually  made,  like 
the  one  on  the  next  page,  of  japanned  copper,  of  tin  plate, 


256.  How  does  oxygen  affect  life  ?     Is  it  poisonous  or  salutary  ? 
257.  What  is  a  pneumatic  trough  ? 


180 


NON-METALLIC    ELEMENTS. 


or  wood,  to  hold  several  gallons  of  water.     The  essential 

parts  are  the  well  (W) 
in  which  the  air-jars  are 
filled,  and  a  shelf  (S) 
covered  with  about  an 
inch  of  water.  A  groove 

W      •Hllllflllll  1 1     or  channel  (d)  is  made 

in  the  shelf,  to  allow  the 
end  of  the  gas-pipe  to 
dip  under  the  air-jar. 
If  nothing  better  is  at 
hand,  a  common  wooden  tub  <w  water-pail,  with  a  perforated 
shelf  and  inverted  funnel,  will  answer  for  small  operations. 
Learners  are  sometimes  puzzled  to  tell  why  the  water  will 
stand  in  an  air-jar  above  the  level  of  the  cistern.  A  moment's 
thought,  however,  on  the  principles  of  atmospheric  pressure 
(24)  already  explained,  will  make  this  clear.  We  must 
remember,  too,  that  gases  are  only  light  fluids,  and  must  be 
poured  upwards,  by  the  same  laws  which  require  fluids 
heavier  than  air  to  be  poured  downwards. 

258.  To  store  large  quantities  of  gases,  capacious  vessels 
of  copper  or  tinned  iron  are  used,  which  are  called  gas- 
holders. These  vessels  are  made  frequently  to  hold  30  to  50 
gallons.  The  simplest  form  is  that  of  a  large  air-jar,  pro- 
vided with  stop-cocks  at  top  for  the  entrance  and  escape  of 
the  gas,  and  contained  in  an  exterior  cask  of  water.  A 
more  convenient  gas-holder  for  some 
purposes  is  that  contrived  by  Mr.  Pepys, 
a  section  of  which  is  shown  in  the 
annexed  figure.  It  is  a  tight  cylinder 
of  copper  or  tin  (#),  with  a  shallow  pan 
of  the  same  metal  supported  above  it  by 
several  props,  two  of  which  are  tubes  with 
stopcocks,  (a  b.)  Near  the  bottom  is  u 
large  orifice  (o)  for  receiving  the  gas.  To 
use  this  instrument,  it  is  first  filled  with 
water  by  closing  the  lower  orifice  (o)  with 
a  large  cork,  and  opening  all  the  upper 
ones,  (a  b  s.)  Water  is  then  poured  into  the  shallow  pan  (p), 
until  it  runs  out  at  s,  which  is  then  closed,  and  the  remainder 


How  arc  gases  poured?     258.  "What  is  a  gas-holder?     Describe 
Pepys'  gas-holder.     How  is  the  gas  introduced  ? 


CHLORINE.  181 

of  the  air  escapes  through  b  ;  when  it  is  full,  the  cocks  (a  b) 
are  shut,  and  the  lower  orifice  being  then  opened,  the  water, 
sustained  by  the  pressure  of  the  air,  cannot  escape  except  as 
it  is  driven  out  by  the  entrance  of  the  gas  at  o,  from  which 
the  water  escapes  as  fast  as  the  gas  enters.  When  used,  the 
gas-holder  must  stand  over  a  tub,  to  catch  the  water  which  is 
driven  out  at  o.  The  gas  is  obtained  for  use  by  drawing  it 
off  from  the  orifice  (s  or  b)  at  the  same  time  that  the  shallow 
pan  (p)  is  full  of  water,  and  the  cock  (a)  open.  The  tube 
to  which  this  cock  is  attached  goes 
nearly  to  the  bottom  of  the  gas-holder, 
and  the  pressure  of  the  water  in  the 
pan  will  force  out  the  gas  from  any 
other  open  orifice  in  the  gas-holder  as 
soon  as  the  cock  (a)  is  opened.  An 
air-jar  is  easily  filled  with  gas  from  the 
holder  by  placing  it  full  of  water  in  the 
upper  pan,  (see  annexed  figure,)  over 
the  orifice  (b) ;  on  turning  the  two  stopcocks,  (a,  b,)  the  gas 
issues  from  b  and  fills  the  jar,  while  the  water  of  the  jar 
runs  down  the  pipe  (a)  to  supply  the  place  of  the  gas. 

In  collecting  gas,  the  precaution  should  never  be  neglected 
of  first  allowing  all  the  atmospheric  air  to  escape  from  the 
vessels,  before  any  of  the  gas  is  saved  for  use. 

Bags  of  India-rubber  cloth  are  prepared  by  the  instrument- 
makers  as  gas-holders,  which  can  be  used  without  the  incon- 
venience of  employing  water. 

259.  Gases  which  are  absorbed  by  water  may  be  collected 
over   mercury ;  but  this  is  an  expensive  method,  because  of 
the  high  cost  of  the  fluid  metal.     Some  gases, — as  chlorine, 
for  instance, — act  on  the  mercury,  forming  compounds  with  it. 
We  may  better  collect  the  absorbable  gases  in  clean  dry 
vessels   by  displacement  of  air,  as  is  explained   by  the  figure 
in  the  next  section. 

CLASS  II. 

2.    CHLORINE. 

Equivalent,  35-41.  Symbol,  Cl.  Density,  2-47. 

260.  History  and  Preparation. — This  very  remarkable 
element  was  first  noticed  by  the  Swedish   chemist,  Scheele, 

How  is  it  prepared  for  use  ?    What  precaution  is  to  be  observed  in 
collecting  gases  ?     259.  How  are  absorbable  gases  collected?     260. 
When  and  by  whom  was  chlorine  discovered  ? 
16 


182 


NON-METALLIC    ELEMENTS. 


in  1774,  while  examining  the  action  of  hydrochloric  acid  on 
peroxyd  of  manganese.  For  a  long  time  it  was  supposed  to 
be  a  compound  body,  but  it  is  now  known  to 
be  simple.  It  is  best  obtained  by  the  action 
of  two  parts  of  hydrochloric  acid  on  one 
part  of  powdered  peroxyd  of  manganese. 
The  materials  are  mingled  in  a  capacious 
flask,  and  the  apparatus  arranged  as  in  the 
figure.  A  drop  or  two  of  oil  of  turpentine 
is  added  to  the  mixture,  to  prevent  the 
frothing  up  of  the  materials.  The  heat  of 
a  lamp,  or  pan  of  coals,  causes  the  gas  to 
pass  over  freely  by  the  bent  tube  to  the 
bottom  of  a  dry  bottle.  This  gas,  being 
much  heavier  than  the  air,  displaces  it 
completely ;  and  when  the  bottle  is  filled, 
(which  we  discern  by  the  greenish  color  of 
the  gas,)  a  greased  stopper  is  tightly  fitted 
to  it,  and  another  bottle  substituted.  In 
this  way  a  number  of  bottles  may  very 
conveniently  be  filled  and  kept  for  use. 
A  card,  with  a  cleft  on  one  side  surrounding  the  tube,  serves 
to  shut  out  fluctuations  of  the  air  while  the  bottle  is  filling.  A 
strong  solution  of  common  salt  (brine)  does  not  absorb  chlo- 
rine, and  may  be  usefully  employed  in  some  cases  to  collect 
this  gas  in  a  small  porcelain  or  other  trough.  It  can  also  be 
collected  with  but  little  loss  in  vessels  filled  with  hot  water. 

In  this  process  the  affinities  are  between  the  manganese, 
for  one  equivalent  of  the  chlorine  in  the  acid,  forming  chlorid 
of  manganese,  and  between  the  oxygen  of  the  manganese 
and  the  hydrogen  of  the  acid,  forming  water.  The  following 
symbols  will  render  this  more  clear :  we  take 

MnO2  and  2HC1,  and  obtain  Mn  Cl,  2HO,  and  Cl. 
The   last  equivalent  of  chlorine,  having   nothing  to  detain  it, 
is  given  ofT.     Chlorine  exists  abundantly  in  sea-water   and 
common  salt,  in  union  with  sodium. 

Pure  chlorine  is  also  easily  obtained  by  acting  on  one  part 
of  powdered  bichromate  of  potash,  in  a  small  retort,  with  six 

How  is  this  gas  obtained  ?  Explain  its  collection  by  displacement. 
How  else  is  it  collected  ?  Explain  the  affinities  which  act  in  the 
collection  of  chlorine.  What  other  method  is  named  for  procuring 
chlorine  ? 


CHLORINE.  183 

parts  of  strong  hydrochloric  acid.  A  gentle  lamp  heat  is 
required  to  begin  the  process,  which  then  goes  on  without 
further  application  of  heat,  yielding  abundance  of  gas. 

261.  Properties.  —  Chlorine    is   a    greenish-yellow   gas, 
(whence  its  name,  from  chloros,  green,)  with  a  powerful  and 
suffocating  odor,  and   is  wholly  irrespirable.     Even  when 
much  diluted  with  air,  it  produces  the  most  annoying  irritation 
of  the  throat,  with  stricture  of  the  chest,  and  a  severe  cough, 
which  continues  for  hours,  with  the  discharge  of  much  thick 
mucus.     The  attempt  to  breathe  the  undiluted  gas  would  be 
fatal ;  yet,  in*&  very  small   quantity,  and  dissolved  in  water, 
it  is  used  with  benefit  by  patients  suffering  under  pulmonary 
consumption. 

Under  a  pressure  of  about  four  atmospheres  it  becomes  a 
limpid  fluid  of  a  fine  yellow  color,  which  does  not  freeze  at 
zero,  and  is  not  a  conductor  of  electricity.  It  immediately 
returns  to  the  gaseous  state  with  effervescence  on  removing 
the  pressure. 

Water  recently  boiled  will  absorb,  if  cold,  about  twice  its 
bulk  of  chlorine  gas,  acquiring  its  color  and  characteristic 
properties.  The  moist  gas  exposed  to  a  cold  of  32°  yields 
beautiful  yellow  crystals,  which  are  a  definite  compound  of 
one  equivalent  of  chlorine  and  ten  of  water,  (C110HO.)  If 
these  crystals  are  hermetically  sealed  up  in  a  glass  tube, 
they  will,  on  melting,  exert  such  a  pressure  as  to  liquefy  a 
portion  of  the  gas,  which  is  distinctly  seen  as  a  yellow  fluid 
not  miscible  with  the  water  which  is  present.  Chlorine  is 
one  of  the  heaviest  of  the  gases,  its  density  being  2-47,  and 
100  cubic  inches  weighing  76-5  grains. 

262.  Its  bleaching  power  is  its  most  remarkable  property, 
and  a  most  valuable  one  in  the  arts,  in  bleaching  rags  for 
paper,  and  in  whitening  linen  and  cotton  goods.     For  these 
purposes,  it  is   procured  in  large  quantities  by  the  action  of 
oil  of  vitriol  on  a  mixture  of  common  salt  and  manganese. 
Either  the  gas  is  used  directly,  or  its  solution  in  water,  or 
its  compound  with  quicklime,  known  as  "  bleaching  powders." 
It  is  easy  to  see  its  power  in  discharging  colors,  by  bleaching 


261.  Describe  chlorine.  How  does  it  affect  respiration?  Under 
what  pressure  does  it  become  fluid  ?  How  does  cold  water  affect  it  ? 
When  moist  chlorine  is  cooled,  what  happens  ?  What  is  the  density 
of  chlorine,  and  weight  of  100  cubic  inches?  262.  What  is  its 
most  remarkable  property  ?  How  is  it  used  for  this  purpose  ? 


184  NON-METALLIC    ELEMENTS. 

some  scraps  of  calico  and  common  writing  on  paper,  in  a 
wine-glass,  by  the  solution  of  the  gas  in  water.  Dry  chlo- 
rine docs  not  bleach,  moisture  being  essential  to  this  process. 
'263.  The  disinfection  of  offensive  apartments,  sewers, 
and  other  like  places,  is  rapidly  accomplished  by  chlorine, 
and  no  other  substance  is  in  this  respect  equal  to  it ;  but  care 
is  required  not  to  use  too  much  of  it  in  apartments  which  arc 
inhabited.  The  bleaching  powder,  mixed  in  shallow  vessels 
with  water,  is  sufficient  for  most  purposes  of  this  nature. 

264.  Double  Condition,  or  Allotropisni  of  Chlorine. — 
Chlorine  can  exist  in  two  states, — an  act i vat  and  a  passive 
state.  The  first  is  its  condition  as  ordinarily  known,  when 
prepared  in  day-light.  If  an  aqueous  solution  of  chlorine 
be  prepared  as  before  mentioned,  in  recently  boiled  water, 
and  a  part  of  it  be  exjx)scd  in  an  inverted  bulb  to  the  direct 
rays  of  the  sun,  or  a  strong  daylight,  while  another  portion* 
as  soon  as  prepared,  without  exposure  to  light,  is  set  aside  in 
a  dark  closet,  and  in  a  similar  vessel,  we  shall  find  them 
very  differently  affected.  That  which  was  in  the  dark  will 
have  undergone  no  change,  while  that  in  the  sun-light 
will  have  suffered  decomposition  ;  a  notable  quantity  of 
nearly  pure  oxygen  will  have  collected  in  the  bulb,  as 
shown  in  the  annexed  figures  and  hydrochloric  acid 
will  have  been  formed  in  the  fluid  from  the  union  of 
the  chlorine  and  the  hydrogen  of  the  water,  whose 
oxygen  is  set  free.  The  rapidity  of  this  decomposition 
of  water  by  the  chlorine  depends  on  the  quantity  of  the  sun's 
rays  and  the  temperature,  and  being  once  begun,  it  continues 
afterwards  even  in  the  dark.  Mere  increase  of  temperature 
does  not,  alone,  cause  the  decomposition,  although  it  aids  it. 
Some  time  elapses  after  the  chlorine  water  is  exposed,  before 
it  begins  to  be  decomposed,  during  which  the  chlorine  is 
undergoing  its  specific  change.  The  indigo  rays  (65)  are 
chiefly  instrumental  in  producing  this  effect,  and  impart  to 
chlorine  an  activity  which  it  does  not  possess  when  kept  in  the 
dark.  The  relations  of  chlorine  to  light  are  very  interesting 
and  important,  and  we  shall  have  something  more  to  say 
about  them  under  hydrogen.  Chlorine,  as  we  shall  see,  is  not 
the  only  element  which  is  known  to  us  in  a  double  condition. 


Does  dry  chlorine  bleach  ?  263.  How  does  it  affect  bad  odors  ? 
264.  Explain  what  is  said  of  the  double  condition  of  chlorine,  and 
the  effect  of  light  on  it. 


CHLORINE.  185 


Compounds  of  Chlorine  with  Oxygen. 

265.  Chlorine  has  comparatively  little  affinity  for  oxygen, 
being  too  closely  allied   to  it  in  general   properties  to  form 
very  stablo  combinations  with  it.     Its  strongest  affinity  is  for 
hydrogen  and  the  metals.     A  lighted  candle  will  burn  with  a 
diminished   flame  in  a  vessel  of  chlorine,  and  an  abundant 
cloud  of  black  smoke  is  given  off,  being  the  carbon  of  the 
flame,  which  cannot  burn  in  chlorine.     A  rag  or  bit  of  paper 
wet  in  oil  of  turpentine,  and  held  in  the  mouth  of  a  bottle  of 
chlorine,  is  inflamed,  while  the  interior  of  the  vessel  is  coated 
with  a  brilliant  black  varnish  of  carbon  derived  from  the  oil. 
In  these  cases  the  chlorine  combines  with  the  hydrogen  of 
the  combustible   body,  and  not  with   the  carbon.     Powdered 
metallic  arsenic,  antimony,  and  some  other  metals,  are  in- 
flamed in  chlorine  gas,  being  converted  into  chlorids.     Phos- 
phorus is  also  spontaneously  inflamed   in  chlorine,  burning 
with  a  pale  yellowish- white   light.     The  strong  affinity  of 
chlorine  for  hydrogen  is  shown  (264)  by  its  power  of  decom- 
posing water  in  the  sun's   light.     The  bleaching  power  of 
chlorine  is  due  probably  to  its  affinity  for  hydrogen.    Printers' 
ink,  of  which   carbon   is  the  basis,  is  not  decolorized   by 
chlorine. 

266.  Chlorine   unites   with   oxygen   only    by   circuitous 
means,  and  forms  with  it  four  compounds,  as  follows : 

Composition  by  weight. 

Symbol.  Chlorine.  Oxygen. 

Hypochlorous  acid,                      CIO  35-41  8 

Chlorous  acid,                                C1O4  3/5-41  32 

Chloric  acid,                                 CIO,  35-41  40 

Hyperchloric  acid,                        C1O7  35-41  56 

267.  Hypochlorous  Acid,   (Euchlorine.) — This  body  is 
always  formed  when  chlorate  of  potash  is  acted  on  by  hydro- 
chloric acid,   but   when  thus   produced  is   almost   instantly 
resolved  into  chlorous  acid  and  chlorine.     The  best  way  to 
procure  it  is  to  pass  a  gentle  stream  of  dry  chlorine  gas  over 


265.  How  are  chlorine  and  oxygen  affected  to  each  other  ?  How 
does  chlorine  affect  burning  bodies,  as  a  candle  ?  Why  is  turpentine 
inflamed  in  it  ?  How  does  it  affect  other  bodies  ?  266.  Name  the 
compounds  of  oxygen  and  chlorine,  and  their  constitution.  267. 
How  is  hypochlorous  acid  formed  ? 

16* 


186 


NON-METALLIC    ELEMENTS, 


red  precipitate,  (the  oxyd  of  mercury  prepared  by  precipi- 
tation,) contained  in 
an  apparatus  similar 
to  the  annexed  fig- 
ure. The  chlorine 
is  evolved  in  the  gas- 
bottle,  (6,)  and  passes 
by  a  bent  tube  to  a 
long  horizontal  tube 
(t)  filled  with  the 
red  precipitate,  with 
which  it  forms  chlo- 
rid  of  mercury, which 
remains  in  the  tube,  while  hypochlorous  acid  (CIO)  is 
evolved  as  a  gas,  and  is  collected  in  a  by  displacement  of  air. 

268.  This    gas   is   of   a    yellowish-green    color,    much 
resembling  chlorine;    water  rapidly  absorbs   100  times   its 
own  volume  of  it.     It  is  easily  exploded   by   heat,  oxygen 
and  chlorine  being  the  result.     At  zero  it  is  condensed  into  a 
deep  red  liquid,  which  is  slowly  dissolved   by  water.     It  acts 
more  corrosively  on  the  skin  than   nitric  acid,  and   bleaches 
powerfully.      Its  aqueous    solution   is  very   unstable,  being 
decomposed  by   light,  and  even   by  agitation  with   irregular 
bodies,  as   broken   glass.     Ilypochlorous  acid   is  one  of  the 
most  powerful  oxydizing  agents  known,  especially  in  raising 
sulphur  and  phosphorus  to  their   highest  state  of  oxydation, 
a  result  which  only  strong  nitric  acid  can  accomplish.     The 
euchlorine  of  Davy  is  a  mixture  of  chlorine  and  chlorous 
acid,  and  not  a  protoxyd  of  chlorine,  as  was  supposed. 

269.  Chlorous  acid,  C1O4. — This    body    is  obtained   by 
the  action  of  sulphuric,  or  of  hydrochloric  acid,  on  chlo- 
rate of  potash.     For  this  purpose  a  little  of  the  salt,  in  a 
small   glass  retort,  is   covered  with   diluted   sulphuric   acid, 
(I  acid  and  £  water,  cooled,)  or  with  its  bulk  of  hydrochloric 
acid,   and  gently   heated   by  a  warm  water  bath.     A  deep 
yellow  gas  is  evolved,  which  may  be  collected   like  chlorine, 
by  displacement  of  air  in   dry  vessels.      It  is  exceedingly 


Explain  the  apparatus.  268.  What  are  the  properties  of  this 
gas  ?  How  does  its  aqueous  solution  behave  ?  Has  it  bleaching 
properties  ?  How  are  its  oxydizing  powers  ?  269.  How  is  chlo- 
rous acid  obtained?  Describe  its  properties.  How  does  it  affect 
combustibles  ? 


CHLORINE.  187 

explosive,  and  will  not  bear  the  heat  of  boiling  water  without 
being  forcibly  resolved  into  its  elements.  A  rag  wet  with 
oil  of  turpentine  at  once  explodes  it.  It  is  composed  of  two 
volumes  of  chlorine  and  four  volumes  of  oxygen,  condensed 
into  four  volumes.  It  is  largely  dissolved  by  water,  forming 
a  rich  yellow  solution  with  bleaching  properties.  It  forms  a 
series  of  salts  with  the  alkalies,  and  is  capable  of  com- 
pression into  a  liquid. 

270.  If   strong   sulphuric  acid    is    poured    upon  a  small 
quantity  of  crystals  of  chlorate  of  potash  in  a  wine-glass,  a 
violent  crackling  is  heard,  and  the  glass  is  soon  filled  with 
the  heavy  yellow  vapors  of  the  chlorous  acid  gas,  which  at 
once  inflame  a  rag  held  over  it  wet  with  turpentine,  with  a 
smart  explosion.     If  the  chlorate  of  potash   is   mixed  with 
sugar,  a  drop  of  sulphuric  acid  will  inflame  the  mixture  with 
a  brilliant  combustion.     Phosphorus  burns  spontaneously  in 
chlorous  acid  gas ;  if  some  small   fragments  of  phosphorus 
are  added  to  a  glass  of  water  at  the  bottom  of  which  a  few 
crystals  of  chlorate  of  potash   have  been   placed,  and  sul- 
phuric acid  is  introduced  by  means  of  a  long-tubed  funnel  to 
the  bottom  of  the  vessel,  the  salt   is  decomposed,  and   the 
phosphorus  flashes  under  water,  in  the  chlorous  acid  which 
is  set  at  liberty. 

271.  Chloric  acid,  C1O5,  is  the  most  important  compound 
of  chlorine  and  oxygen.     It  is  formed   by   passing  chlorine 
gas   through  a  solution  of  pure   potash,  to  saturation  ;    on 
evaporating  this  solution,  flat  tabular  crystals  of  a  white  salt 
are  gradually  formed,  which  are  chlorate  of  potassa,  while  a 
chlorid  of  potassium  remains  in  the  solution.     This  important 
salt,  as  already  mentioned,  (253,)  is  a  compound  of  chloric 
acid  and  potassa,  (C1O5KO.)     The  acid  is  obtained  separate 
and  pure  with  some  difficulty,  by  decomposing  a  solution  of 
chlorate  of  baryta  by  the  requisite  amount  of  sulphuric  acid, 
and  gradually  evaporating  the   liquid  to  a  syrup.     In   this 
state  its  affinity  for  all  combustible  matter  is  so  great,  that  it 
cannot  be  kept  for  an  instant  in  contact  with  any  substance 
containing  carbon  or   hydrogen.     The  chlorates  are  at  once 


How  does  heat  affect  it  ?  270.  What  happens  when  chlorate  of 
potash  is  treated  with  strong  sulphuric  acid  ?  How  is  the  com- 
bustion of  phosphorus  shown  by  it  under  water?  271.  Describe 
the  formation  of  chloric  acid.  What  use  has  already  been  made  by 
us  of  its  compound  with  potash?  What  are  its  characteristic 
properties  ? 


188  NON-METALLIC    ELEMENTS. 

recognised  by  their  powerful  action  on  combustible  matter, 
by  yielding  pure  oxygen  when  heated,  and  by  giving  out  the 
yellow  chlorous  acid  when  treated  with  sulphuric  acid. 

3.    BROMINE. 

Equivalent,  78'26.  Symbol,  Br.  Density,  in  vapor,  5*93. 

272.  History. — This  element  was  discovered  in  1826,  by 
M.  Balard,  in  the  mother-liquor,  or  residue  of  the  evaporation 
of  sea-water.     It  is  named  from  its  offensive  odor,  (bromos, 
bad  odor.)     In  nature  it  is  found  in  sea-water  combined  with 
alkaline  bases,  and  in  the  waters  of  many  saline  springs  and 
inland  seas.     The  salt  springs  of  Ohio  abound   in   the  com- 
pounds of  bromine,  and  it  is  found  in  the  waters  of  the  Dead 
Sea.     The  only  use  which  has  been  made  of  bromine  in  the 
arts  is  in  the  practice  of  photography.     It  is  also  used  in 
medicine.     In  a  chemical  point  of  view  it  is  very  interesting, 
from  its  similarity  in  properties,  and   the  parallelism  of  its 
compounds  to  chlorine  and  iodine. 

273.  Preparation. — The  mother-liquor  containing  bromids 
is  treated  with  a  current  of  chlorine  gas,  which  decomposes 
these  salts,  setting  the  bromine  free,  which  at  once  colors  the 
liquid  of  a  reddish-brown  color.     Ether  is  added  and  shaken 
with  the  liquid,  until  all  the  bromine  is  taken  up  by  the  ether, 
which  acquires  a  fine  red  color,  and  separates  from  the  saline 
liquid.     Solution  of  caustic   potash    is   then   added    to   the 
ethereal   solution,  forming  bromid  of  potassium  and  bromate 
of  potash.     This  solution  is  evaporated  to  dryness,  and  the 
salts   being  collected   arc   heated  in  a  glass  retort  with  sul- 
phuric acid  and  a  little  oxyd  of  manganese.     The  bromine 
distils  over,  (117,)   and  is  condensed  in  a  cooled   receiver, 
into  a  red  fluid. 

274.  Properties. — Bromine  somewhat  resembles  chlorine 
in  its  odor,  but  is  more  offensive.     At  common  temperatures 
it  is  a  very  volatile  liquid,  of  a  deep  red  color,  and  with  a 
specific  gravity  of  3,  being  one  of  the  heaviest  fluids  known. 
Sulphuric  acid  floats  on  its  surface,  and  is  used  to  prevent  its 
escape.     At  zero  it  freezes  into  a  brittle  solid.     A  few  drops 

272.  When,  where,  and  by  whom,  was  bromine  discovered  ? 
Whence  its  name  ?  How  is  it  found  in  nature  ?  What  use  is  made 
of  it?  273.  Describe  its  preparation.  274.  Describe  its  properties. 
How  does  it  resemble  chlorine  ? 


IODINE.  189 

.*.n  a  large  flask  will  fill  the  whole  vessel  when  slightly 
warmed,  with  blood-red  vapors,  which  have  a  density  of 
nearly  6*00,  air  being  one.  It  is  a  non-conductor  of  elec- 
tricity, and  suffers  no  change  of  properties  from  heat,  or  any 
other  of  the  imponderable  agents.  It  dissolves  slightly  in 
water,  forming  a  bleaching  solution. 

Bromine  unites  with  oxygen,  forming  bromic  acid, 
(BrO5,)  which  is  similar  in  all  its  actions  to  chloric  acid. 
It  forms  salts  with  alkaline  bases,  which  are  called  bromates. 

4.    IODINE. 

Equivalent ,  126*36.  Symbol,  I.  Density  in  vapor,  8-7. 

275.  History. — Like  chlorine  and  bromine,  this  substance 
has  its  origin  in  the  sea,  being  secreted  by  nearly  all  sea- 
weeds from  the  waters  of  the  ocean.     It  was  discovered  in 
1811,  by  M.  Courtois,  of  Paris,  in  the  kelp,  or  ashes  of  sea- 
weeds.    The  common  bladder  sea-weed,  (fucus  vesiculosus,} 
and  many  other  sea- weeds  of  our  own  coasts,  abound  in  salts 
of  iodine.     It   has   been   found   in  mineral  springs   rather 
abundantly,  and  in  one  or  two  minerals.     In  the  arts  its 
chief  uses  are  for  the  photographic  pictures,  and  lately  it  has 
been  employed  in  France  in  the  process  of  dyeing.     In  medi- 
cine it  is  of  great  value  in  glandular  and  other  diseases. 

276.  Preparation.  —  Kelp  is  treated   with  water,  which 
washes  out  all  the  soluble  salts,  and  the  filtered  solution  is 
evaporated  until  nearly  all  the  carbonate  of  soda  and  other 
saline  matters  have  crystallized  out.     The  remaining  liquor, 
which  contains  the  iodine,  is  mixed  with  successive  portions 
of  sulphuric,  acid  in  a  leaden  retort,  and  after  standing  some 
days  to  allow  the  sulphuretted  hydrogen,  &c.,  to  escape, 
peroxyd  of  manganese  is  added,  and  the  whole  gently  heated. 
Iodine  distils  over  in  a  purple  vapor,  and  is  condensed   in  a 
receiver,  or  in  a  series  of  two-necked  globes. 

277.  Properties.  —  Iodine   crystallizes  in    brilliant   blue- 
black  scales  of  a  metallic  lustre,  somewhat  resembling  plum- 
bago.    When  slowly  cooled  from  a  state  of  dense  vapor  in  a 
glass  tube  hermetically  sealed,  it  crystallizes  in  acute  octa- 

275.  How  is  iodine  found  associated  ?  Who  discovered  it,  and 
when?  What  are  its  uses?  Does  it  unite  with  oxygen?  276. 
How  is  it  prepared?  277.  Describe  its  properties?  How  does  it 
crystallize  ? 


190  NON-METALLIC    ELEMENTS. 

hedrons  with  a  rhombic  base,  (222.)  The  density  of  iodine 
is  3-948,  (water  =  1,)  it  melts  at  225°,  and  boils  at  247°, 
forming  a  superb  violet  vapor  of  unequalled  beauty  ;  (hence 
its  name,  iodes,  like  a  violet.)  For  this  purpose  a  few  grains 
of  it  may  be  volatilized  in  a  bolt-head,  (74,)  or  on  a  piece  of 
heated  brick.  If  a  small  portion  is  thrown  into  a  red-hot 
platinum  crucible,  it  at  once  assumes  the  spheroidal  state, 
(135,)  and  will  roll  about  in  a  liquid  globule  and  give  off 
very  little  vapor.  If  the  crucible  is  then  allowed  to  cool  to 
about  220°,  it  suddenly  bursts  into  a  cloud  of  purple  vapor, 
forming  a  most  striking  and  instructive  experiment. 

Iodine  is  almost  insoluble  in  pure  water,  requiring  7000 
parts  of  water  to  dissolve  one  of  iodine,  or  one  grain  to  a 
gallon  of  water.  Alcohol  and  ether  dissolve  it  freely,  and 
so  do  solutions  of  nitrate  or  hydrochlorate  of  ammonia,  and 
of  iodids.  It  temporarily  stains  the  skin  deep  brown,  and  its 
odor  reminds  us  of  chlorine,  but  it  is  much  less  annoying. 

Iodine  forms  a  deep  blue  compound  with  a  cold  solution 
of  common  starch,  by  which  it  may  at  once  be  detected,  this 
being  a  characteristic  test.  In  combination  it  may  be  de- 
tected by  the  same  agent,  if  a  little  nitric  acid  or  chlorine 
water  is  previously  added  to  the  fluid  supposed  to  contain  an 
iodid,  whereby  the  iodine  is  set  free. 

Compounds  of  Iodine  with  oxygen. 

278.  Iodine  unites  with  oxygen,  forming  iodic  and 
hyperiodic  acids.  Their  constitution  is  seen  in  the  following 
formulae. 

Composition  by  weight. 

Symbol.  Iodine.  Oxygen. 

Iodic  acid,  IO5  126-36  40 

Hyperiodic  acid,  10?  126-36  56 

These  acids  are  analogous  to  the  chloric  and  perchloric 
acids.  Iodic  acid  is  formed  by  the  action  of  strong  nitric 
acid  on  iodine,  and  subsequent  evaporation,  to  expel  the  free 
nitric  acid  remaining.  It  is  a  very  soluble  substance,  and 
crystallizes  in  six-sided  tables. 


Give  its  density  in  vapor,  and  as  a  solid  its  point  of  fusion.     In 
what  is  it  soluble  ?     By  what  easy  test  is  it  detected  ?     278.  What 
compound  does  it  form  with  < 
formulae.     To  what  are  these 
pounds  of  iodine  and  oxygen  ? 


compound  does  it  form  with  oxygen  ?     Give  their  composition  and 
formulas.     To  what  are  these  acids  analogous?     What  are  the  com- 


FLUORINE.  191 

279.  Both    bromine   and   iodine   combine  with  energetic 
combustion    or    explosive    violence   with    phosphorus,   and 
several  of  the  metals,  forming  bromids  and  iodids  with  such 
bases.     Chlorine  unites  with  iodine,  forming  two,  and  pos- 
sibly three  distinct  chlorids,  (IC1,  IC13,  and  IC15.)     These  are 
formed  by  the  direct  action  of  chlorine  on  dry  iodine.     There 
are  also  bromids  of  iodine  of  uncertain  composition. 

5.    FLUORINE. 

Equivalent,  18-70.    Symbol,  F.    Density,  1-289. 

280.  History  and  Properties. — This  element  has  only 
very  lately  been  obtained  in  a  free  state,  although  we  have 
long  known  its  compounds.     Its  remarkable  energy  of  com- 
bination with  the  metals,  and  especially  with  silicon,  which 
is  a  constituent  of  all  glass,  has  rendered  its  isolation  very 
difficult.     Messrs.    Knox,  of  Ireland,   and   Baudrimont,  of 
France,  have  so  far  succeeded  in  effecting  its  separation  as 
to  leave  no  doubt  of  its  being  a  yellowish-brown  gas,  having 
the  smell  and  bleaching  properties  of  chlorine.     It  does  not 
act  on  glass,  (as  its  compound  with  hydrogen  does,)   but 
unites  directly  with  gold.     Its  specific  gravity  is  1-289.     Its 
associations   and    characteristic    properties   all    show    most 
decidedly  that  it  must  be  classed  with  this  group  of  elements, 
and  it  is,  in  common  with  its  associates,  a  powerful  negative 
electric.      Fluorine    probably    holds   a   place    intermediate 
between  oxygen  and  chlorine.     The  fact  that  it  forms  no 
known  compound  with  oxygen  shows  how  very  similar  in 
character  it  must  be  to  that  element* 

281.  The  compounds  of  fluorine,  which  we  shall  mention, 
nearly  all  belong  to  subsequent  groups,  although  it  forms  no 
known  compound  with  oxygen ;  Mr.  Leeson  has  recently  suc- 
ceeded in  combining  it  with  iodine  and  bromine.    When  a  mix- 
ture of  fluor-spar  with  peroxyd  of  manganese  and  sulphuric 
acid  is   heated,  a  reaction  takes  place,  by  which  fluorine  in 
an  impure  form  is  disengaged.     If  the  gas  thus  produced  is 
passed  through  iodine  suspended  in  water,  combination  takes 


279.  How  are  bromine  and  iodine  affected  by  phosphorus  and  the 
metals?  Does  chlorine  unite  with  iodine?  280.  What  has  pre- 
vented the  study  of  fluorine  ?  What  is  Icnown  of  it  ?  To  what  is 
it  allied  closely  ?  Does  it  unite  with  oxygen  ?  2S1.  What  com- 
pounds of  it  are  named  in  this  section  ? 


192  SULPHl'R. 

place,  and  a  fluorid  of  iodine  is  formed,  which  crystallizes  in 
yellow  scales.  A  fluorid  of  bromine  is  formed  by  a  similar 
process,  which  has  been  used  in  the  photographic  art  with 
success.  It  is  not  crystallizable.  The  precise  composition 
of  these  bodies  is  not  known. 

CLASS  III. 

6.    SULPHUR. 

Equivalent,  16-09.   Symbol,  S.  Density  in  vapor,  6-648. 

262.  History. — Sulphur  is  one  of  those  elements  which 
have  been  known  from  the  remotest  antiquity.  It  occurs 
abundantly  in  many  volcanic  regions,  as  in  the  island  of 
Sicily,  the  vicinity  of  Naples,  and  many  islands  of  the 
Pacific.  It  is  also  found  in  beds  of  gypsum,  as  n  rock,  near 
Cadiz  in  Spain,  and  at  Cracow  in  Poland.  Its  compounds 
with  iron,  copper,  and  other  metals,  are  widely  spread  over 
the  earth,  and  in  combination  as  sulphuric  acid  it  forms  a 
large  part  of  common  gypsum  or  plaster  of  Paris. 

Properties.  —  It  is  a  straw-yellow  brittle  solid  at 
common  temperatures,  having  a  gravity  of  T9^. 
In  crystalline  form  it  is  dimorphous,  (233.)  Its 
usual  form  is  the  rhombic  octahedron,  (222,)  as  in 
the  figure.  Xatire  sulphur  has  this  form  or  its 
modification,  and  so  has  sulphur  deposited  in  crys- 
tals from  solution.  Hut  if  it  is  fused  (as  in  a 
crucible)  and  allowed  to  cool  gradually,  and  the 
crust  is  broken  t*fore  the  whole  of  the  interior  mass 
is  solidified,  a  part  may  l>e  turned  out,  while  the  remainder 
has  the  form  of  long,  slender,  confused 
prisms,  as  in  the  annexed  figure.  This 
dillerence  of  form  is  the  result  of  tempe- 
rature. Sulphur  melts  at  226°,  and  from 
that  point  to  2SO°  is  a  clear  amber-colored 
fluid.  At  about  320°  it  begins  to  thicken 
and  grow  reddish,  and  from  that  point  to 
about  480°  it  is  so  stiff  that  the  vessel 
containing  it  may  be  turned  over  without  spilling  it.  In  this 
state  it  copies  seals,  medallions,  &c.,  very  perfectly,  and  is 

2S2.  Give  the  natural  history  of  sulphur.  283.  What  are  its 
principal  properties?  Describe  its  crystallization  and  fusion. 


SULPHUR.  193 

much  used  for  this  purpose.  At  482°  it  becomes  more  fluid, 
and  remains  so  until  it  reaches  its  boiling  point  at  601°.  It 
is  very  volatile,  and  sublimes  readily  even  below  its  boiling 
point,  forming  flowers  of  sulphur.  This  is  the  method  used 
to  purify  it  from  the  earthy  matters  found  with  it.  It  is  also 
cast  into  long  cylinders,  and  is  then  called  roll  sulphur. 
When  cold  it  has  no  odor,  and  the  warmth  of  the  hand  causes 
it  to  crackle,  from  a  disturbance  of  its  crystalline  structure. 
By  warmth  and  friction  it  acquires  its  weM  known  brimstone 
smell.  It  is  eminently  a  non-conductor  of  electricity,  and  is 
easily  excited  to  give  negative  electrical  sparks  by  friction. 

Sulphur  is  insoluble  in  water,  and  tasteless.  It  is  dissolved 
by  oil  of  turpentine,  and  some  other  oils,  and  more  readily 
in  sulphuret  of  carbon.  Its  vapor  is  soluble  in  vapor  of  alco- 
hol, but  fluid  alcohol  docs  not  dissolve  solid  sulphur. 

284.  In  its  chemical  relations  it  much  resembles  oxygen. 
It   forms  sulphurcts  with   most  of  the  elements    that   form 
oxyds,    and    these    sulphurets    often   unite    to    form    bodies 
analogous  to  salts,  as  the  oxyds  do.     Bcrzelius  with  much 
reason  argues  that  its  binary  combinations,  from  their  analogy 
to  the  oxyds,  should  be  called  sitlphids,  and  not  sulphurets. 

Its  uses  are  well  known.  It  is  one  of  the  essential  ingre- 
dients of  gunpowder,  and  is  the  basis  of  all  kinds  of  matches. 
Nearly  all  the  sulphuric  acid  used  in  the  arts  is  made  from 
it.  The  gas  arising  from  its  combustion  is  employed  in 
bleaching  straw  and  woolen  goods ;  and  in  medicine  it  has  a 
specific  power  in  certain  obstinate  cutaneous  diseases. 

Compounds  of  Sulphur  with  Oxygen. 

285.  With  oxygen  it  unites   in   several   proportions.     It 
burns  in  common  air  with  a  pale  blue  flame,  and  gives  the 
well  known  odor  of  a  burning  match,  forming  only  sulphurous 
acid,  which  is  its  lowest  compound  with  oxygen.     Tho»  com- 
pounds of  sulphur  and  oxygen  are  numerous,  but  only  two 
of  them  are  of  sufficient  importance  to  engage  our  attention 
at  present,  viz  : — 


Is  it  volatile  ?  Has  it  odor  when  cold  ?  How  does  it  act  as  an 
electric  ?  In  what  is  it  soluble  ?  284.  What  are  its  chemical 
relations  ?  Why  is  it  associated  with  oxygen  ?  Name  its  uses. 
285.  What  compounds  does  it  form  with  oxygen  ? 

17 


194-  NON-METALLIC    ELEMENTS. 

Combination  by  weight. 

Symbol.  Sulphur.         Oxygen. 

Sulphurous  acid,  SO2  16-09  16 

Sulphuric  acid,  S03  16-09  24 

286.  (1.)  Sulphurous  acid,  (SO2.)— This  is  the  sole  pro- 
duct  of  the  combustion  of  sulphur  in  common  air  or  pure 
oxygen  gas.     But  for  experiment  it  is  prepared  by  the  action 
of  sulphuric  acid  (SO3)  with   heat  on  copper  clippings  or 
mercury,  in  a  glass  retort.     One  equivalent  of  oxygen   is 
retained  by  the  metal,  and  the  other  two  with  the  sulphur  are 
given  off  as  sulphurous  acid.     Sulphurous  acid  is  one  of  the 
gases  which  must  be  collected  over  mercury,  or  by  displace- 
ment of  air  in  dry  vessels.     Its  high  specific  gravity  renders 
it  easy  to  do  the  latter. 

287.  Properties. — This  is  a  colorless  gas,  having  a  density 
of  2-21  :  100  cubic  inches  of  it  weigh  68-69  grains.     It  has 
a  very  pungent,  suffocating  odor,  quite  insufferable,  and  it  at 
once  extinguishes  flame.     A  lighted  candle  lowered  into  a 
jar  containing  it  is  extinguished,  and  the  edges  of  the  flame, 
as  it  expires,   are  tinged   with   green.     A  solution  of  blue 
litmus  or  blue  cabbage  turned  into  a  jar  of  the  gas  is  at  first 
reddened   by  the  acid,  and   then   bleached.     Water  absorbs 
37  times  its  volume  of  sulphurous  acid,  forming  a  strongly 
acid  fluid.     Its  avidity  for  moisture  is  so  great  that  it  forms 
an  acid  fog  with  the  water  in  the  atmosphere,  and  a  bit  of  ice 
slipped  under  a  jar  of  it  on  the  mercurial  cistern  is  instantly 
melted ;  the  water  absorbs  the  gas,  and  the  mercury  rises  to 
fill  the  jar.    Its  bleaching  power  is  only  temporary.    Articles 
bleached  by  it  after  a  time  regain  their  previous  color. 

288.  Sulphurous  acid  is  easily  condensed  by  cold  and 
pressure  into  a  fluid  having  a  specific  gravity  of  1*45,  which 
becomes  a  crystalline,  transparent,  colorless  solid  at  — 105°. 
The  solid  is  heavier  than  the  liquid,  and  sinks  in  it. 

By  volume,  sulphurous  acid  contains  one  volume  of  oxygen 
and  £  volume  of  sulphur  vapor,  (191,)  condensed  into  one 
volume.  Sulphurous  acid  forms  a  series  of  salts  with  bases, 
which  are  called  sulphites. 


28G.  How  is  sulphurous  acid  formed?  How  is  it  collected? 
287.  Give  its  properties.  Does  it  support  the  combustion  of  a- 
candle  ?  How  does  it  affect  vegetable  colors  ?  Is  it  dissolved^  by 
water  ?  What  of  its  avidity  for  moisture  ?  Does  it  bleach  perma- 
nently ?  288.  Does  it  become  liquid  ?  At  what  temperature  is  it 
solid  ?  Give  its  composition  by  volume. 


SULPHUR. 


195 


289.  (2.)  Sulphuric  acid,  (SO3 ,  HO.)— This  acid  is  one 
of  the  most  important  compounds   known ;  its  affinities  are 
very  powerful,  and  no  class  of  bodies  is  better  understood  by 
chemists  than  the  sulphates.     In  the  arts  great  use  is  made 
of  sulphuric  acid,  many  millions  of  pounds  of  it  being  annually 
consumed  in  manufacturing  nitric  and  muriatic  acids,  the  sul- 
phate of  copper,  and  alum,  and  in  the  processes  of  dyeing. 

It  is  not  formed  by  the  direct  union  of  its  elements,  since 
we  have  seen  that  only  sulphurous  acid  can  result  from  the 
combustion  of  sulphur  in  air.  Sulphurous  acid  must  be 
oxydized  to  form  sulphuric  acid. 

290.  This  may  be  done  by  passing  a  mixture  of  sulphu- 
rous acid  with  common  air  over  spongy  platinum,  heated  to 
redness  in  a  tube,  when  there  will  issue  from  the  open  end  of 
the  tube  a  mixture  of  sulphuric  acid  in  vapor,  with  nitrogen 
from  the  air.     In  the  arts,  however,  this   process   cannot  be 
used  ;  but  sulphuric  acid  is  made  on  a  large  scale  by  bringing 
together  sulphurous   acid,  (SO2,)  nitrous  acid,  (NO4,)  and 
water,  (HO,)  all  in  a  state  of  vapor,  in  a  large  chamber  or 
room,  when  sulphurous  acid  (SO2)  passes  to  a  higher  state 
of  oxydation  (SO3)  at  the  expense  of  one  half  the  oxygen  of 
the  nitrous  acid,  (NO4,)  which  thus-  becomes  reduced  to  the 
state  of  the  deutoxyd 

of  nitrogen,  (N02.) 
The  arrangement 
employed  is  repre- 
sented in  the  an- 
nexed figure.  A  A 
is  a  chamber  fifty 
feet  or  more  long, 
lined  on  all  sides 
with  sheet  lead.  A 
very  large  leaden 
tube  (B)  opening 
into  one  end  of  the 
chamber,  communicates  with  a  furnace.  Its  lower  end 
rests  in  a  gutter  (o  o)  of  dilute  acid,  to  prevent  the  effects  of 


289.  What  is  said  of  the  importance  of  sulphuric  acid  ?  What 
are  its  chief  uses  in  the  arts  ?  How  is  it  formed  ?  290.  How  may 
sulphurous  acid  be  oxydized  ?  How  is  it  done  in  the  arts  ?  Of 
what  use  are  the  nitric  and  nitrous  acids,  in  this  process  ?  Describe 
the  arrangement  of  the  leaden  chamber. 


196  NON-METALLIC    ELEMENTS. 

too  much  heat,  and  the  escape  of  the  vapors.  The  sulphur 
is  intioduced  by  a  door  (c)  to  an  iron  pan,  and  a  fire  built 
beneath,  (n.)  The  heat  melts  the  sulphur,  which  burns  in  a 
current  of  air  passing  over  it,  and  the  sulphurous  acid  thus 
formed  enters  the  chamber  in  company  with  air  and  the 
vapors  of  nitric  acid  set  free  from  small  iron  pans  standing 
over  the  sulphur,  and  containing  the  materials  to  evolve 
nitric  acid,  (sulphuric  acid  and  saltpetre.)  A  small  steam- 
boiler  (e)  furnishes  a  jet  of  steam  (x)  as  required,  and  a 
quantity  of  water  covers  the  floor,  which  is  inclined  so  as  to 
be  deepest  at  h.  A  chimney  with  a  valve  or  damper  (p) 
allows  the  escape  of  spent  and  useless  gases.  Things  being 
thus  arranged,  the  chamber  receives  a  constant  supply  of 
sulphurous  acid,  common  air,  nitric  acid-vapor,  and  steam. 
These  react  on  each  other ;  the  nitric  acid  (NO5)  gives  up  a 
part  of  its  oxygen  to  the  sulphurous  acid,  forming  nitrous 
acid,  (NO4,)  and  finally  the  deutoxyd  of  nitrogen,  (NO2.) 
The  last  substance  in  contact  with  air  gaihs  another  equiva- 
lent of  oxygen,  to  form  nitrous  acid  anew,  which  is  again 
destined  to  be  deoxydized  by  a  fresh  portion  of  sulphurous 
acid.  In  this  way  a  small  quantity  of  nitric  acid  can  be 
made  to  oxydize  an  indefinite  amount  of  sulphurous  acid ; 
serving  the  purpose,  as  it  were,  of  a  carrier  of  oxygen  from 
the  atmospheric  air  to  the  sulphurous  acid.  Meanwhile  the 
water  on  the  floor  of  the  chamber  grows  rapidly  acid ;  and 
when  it  has  attained  a  specific  gravity  of  about  1'5,  it  is 
drawn  off  and  concentrated  by  boiling,  first  in  open  pans  of 
lead  until  it  becomes  strong  enough  to  corrode  the  lead,  and 
afterwards  in  stills  of  platinum  until  it  has  a  density  of  about 
1-8,  in  which  state  it  is  sold  in  carboys,  or  large  bottles 
packed  in  boxes. 

291.  The  process  of  forming  sulphuric  acid  is  easily 
illustrated  in  the  class-room,  by  an  arrangement  of  apparatus 
like  that  shown  in  the  adjoining  figure.  Two  flasks  (a  b) 
are  so  connected  by  bent  tubes  with  a  large  bottle,  that  from 
one  (a)  sulphurous  acid,  and  from  the  other  (b)  nitric  oxyd 


What  vapors  enter  the  chamber  ?  What  use  is  made  of  steam  ? 
What  receives  and  condenses  the  vapors  ?  Explain  the  successive 
changes  which  take  place  in  the  chamber.  How  can  a  small  quan- 
tity of  nitric  acid  answer  the  purpose  ?  How  is  the  acid  water 
from  the  chamber  concentrated?  291.  How  can  we  illustrate  this 
process  in  the  class-room  ? 


SULPHUR. 


197 


gases  (304)  are  made  to  pass  into  the  middle  bottle,  the  inner 
surface  of  which  is  slightly  moistened.  By  blowing  in 
occasionally  at  c,  the  spent  gases  are  ejected  at  d,  and  fresh 
air  introduced.  Under  these  circumstances  the  interior  of 
the  central  vessel  is  soon 
covered  with  a  white  crys- 
talline solid,  which' appears 
to  be  a  compound  of  sul- 
phurous acid  and  nitrous 
acid,  (SO2,NO4.)  This 
substance  is  decomposed 
by  a  larger  quantity  of 
water  into  sulphuric  acid 
and  hyponitrous  acid,  and 
as  it  is  known  to  be  formed 
in  the  leaden  chambers  in 
large  quantities,  it  is  supposed  to  have  an  important  influence 
in  the  production  of  sulphuric  acid. 

292.  Sulphuric  acid  unites  with  water  in  four  proportions ; 
namely, 


Nordhausen  acid, 
Oil  of  vitriol, 
Acid  of  sp.  gr.,  1-78, 
Acid  of  sp.  gr.,  1'63, 


2(S03)HO 
S03,HO 
S03,HO-fHO 
S03,HO  +  2H 


293.  The  most  concentrated  sulphuric  acid,  however,  is 
made  by  distilling  dry  sulphate  of  iron  in  earthenware 
retorts,  at  a  red  heat,  when  the  acid  of  the  salt  with  half  an 
equivalent  of  water  comes  over  in  vapor,  and  is  condensed 
in  earthen  tubes.  It  is  a  dark-brown,  oily  fluid,  of  the 
specific  gravity  of  1*9,  or  nearly  twice  as  heavy  as  water, 
and  with  such  an  avidity  for  water  as  to  hiss  like  hot  iron 
'when  dropped  into  it.  This  sort  of  acid  is  made  at  Nord- 
hausen, in  Saxony,  and  is  commonly  called  the  Nordhausen 
sulphuric  acid.  It  has  the 'composition  of  2SO3,HO  =  89-19. 
When  it  is  put  in  a  retort  and  moderately  heated,  a  white 
crystalline  product  is  obtained  from  it,  which  is  dry,  or  anhy- 


Explain  the  arrangement  and  reaction.  What  is  the  composition 
of  the  white  crystalline  compound  ?  How  does  water  affect  it  ? 
292.  What  compounds  does  sulphuric  acid  form  with  water?  293. 
How  is  the  strongest  sulphuric  acid  made  ?  What  is  its  character  ? 
its  strength  ?  its  formula  ?  What  is  it  called  ? 

17* 


198  NON-METALLIC    ELEMENTS. 

drous  sulphuric  acid,  (SO3.)  Common  sulphuric  acid,  when 
as  strong  as  possible,  has  still  one  equivalent  of  water,  as 
above.  It  also  unites  with  two  equivalents,  (SO3,lIO-f  HO,) 
with  a  specific  gravity  of  1-780.  When  acid  of  this  strength 
is  exposed  to  a  temperature  of  32°,  it  freezes  in  large  crys- 
tals. Great  heat  is  generated  from  the  mixture  of  strong 
sulphuric  acid  and  water,  and  a  diminution  of  bulk  attends 
the  mixture.  When  exposed  to  a  temperature  of  15°,  sul- 
phuric acid  freezes ;  and  at  620°  it  boils,  giving  off  a  dense 
white  vapor.  It  is  intensely  acid  to  the  taste,  and  deadly, 
if  by  any  accident  it  is  swallowed,  corroding  and  burning  the 
organs  with  intense  heat.  It  blackens  nearly  all  inorganic 
matters,  charring  or  burning  them  like  fire.  Its  strong  dis- 
position for  water  enables  us  to  employ  it  in  desiccation,  and 
in  the  absorption  of  aqueous  vapor,  (122.) 

294.  The  silky  anhydrous  compound  (SO3)  obtained  from 
the  distillation  of  Nordhausen  acid,  (2SQj,-f-HO,)  does  not 
possess  acid  properties  when  dry,  but  water  at  once  changes 
it  to  common  sulphuric  acid.     It  has  therefore  been  inferred 
that  sulphuric  acid  cannot  exist  without  water,  or  that  water 
is  essential  to  the  acid  property.     In  this  case  it  is  supposed 
that  the  oxygen  of  the  water  joins  that  already  with  the  sul- 
phur, (forming  SO4,)  while  the  new  compound  thus  produced 
unites  with  hydrogen,  forming  SO4H.     Some  writers  prefer 
to  express   the  composition   of  sulphuric  acid  in  this  way, 
because  it  commits  them  to  no  theory,  but  is  merely  a  state- 
ment of  the  number  of  atoms  of  each  element  in  the  com- 
pound, without  attempting  to  decide  how  the  elements  may 
be  united. 

295.  Chlorid   of  sulphur   is    prepared    by   passing   dry 
chlorine  over  melted  sulphur.     It  is  a  volatile,  deeply-colored 
liquid,  of  a  disagreeable  odor,  boils  at  280°,  and  has  a  density 
of  1-687.     It  consists  of  two  equivalents  of  sulphur  and  one 
of  chlorine,  (S2C1.)     It  is  decomposed  by  water. 

There  are  also  bromids  and  iodids  of  sulphur,  which  how- 
ever possess  very  little  interest. 


Give  the  composition  of  the  common  sulphuric  acid.  At  what 
strength  and  temperature  does  it  freeze  ?  When  mingled  with 
water,  what  happens  ?  Give  other  properties  of  sulphuric  acid. 
294.  Is  the  silky  compound  acid  ?  To  what  does  the  common  acid 
owe  its  acid  properties  ?  What  view  is  given  of  the  possible 
arrangement  of  its  atoms  ?  295.  What  compounds  of  sulphur  are 
here  named  ? 


SELENIUM.  199 

7.    SELENIUM. 

Equivalent,  39'57.    Symbol,  Se.    Density,  4*3. 

296.  History  and   Properties. — This  element  was  dis- 
covered by  Berzelius  in   1818,  and  named    by   him  from 
selene,  the  moon.     It  is  associated  in  nature  with  sulphur  in 
some  kinds  of  iron  pyrites,  and  also  at  the  Lipari  Islands 
combined  with  sulphur  and  accompanied  by  other  volcanic 
products. 

It  closely  resembles  sulphur  in  most  of  its  properties,  as 
well  as  in  its  natural  associations.  At  common  temperatures 
it  is  a  brittle  solid,  opake,  and  having  a  metallic  lustre  like 
lead,  but  in  powder  it  is  of  a  deep  red  color.  Its  specific 
gravity  is  between  4*3  and  4-32.  It  softens  at  212°,  and 
may  then  be  drawn  out  into  red  colored  threads ;  at  a  little 
higher  temperature  it  melts  completely,  and  boils  at  650°r 
giving  a  deep  yellow  vapor  without  odor.  It  is  insoluble. 
When  heated  in  the  air,  it  combines  with  oxygen  and  gives 
out  a  disagreeable  and  strong  odor,  like  putrid  horse-radish. 
Before  the  blowpipe,  on  charcoal,  it  burns  with  a  pale  blue 
flame,  and  -Jg-  of  a  grain,  so  heated,  will  fill  a  large  apart- 
ment with  its  odor.  It  is  a  non-conductor  of  heat  and  of 
electricity. 

297.  The  compounds  of  selenium  with  oxygen  are  three, 
two  of  which  are  acids  analogous  to  sulphurous  and  sulphu- 
ric acids.     Their  composition  is, 

Composition  by  weight. 

Symbol.  Selenium.  Oxygen. 

Oxyd  of  selenium,                 SeO  39-57  8 

Selenious  acid,  .                     SeO2  39-57  16 

Selenic  acid,                            Se03  39.57  24 

298.  Oxyd   of   selenium   is   formed    when    selenium    is 
heated   in  the  air.     It  is  a  colorless  gas,  and  possesses  the 
strong  odor   before  mentioned.     Selenious  acid  is  a  white 
and  very  soluble  body,  procured  by  the  action  of  nitric  acid 
on   selenium.     It  is   distinctly  acid,  and   can   be   sublimed 


296.  When,  where,  and  by  whom  was  selenium  discovered  ? 
Give  its  properties.  What  physical  property  most  distinguishes  it  ? 
297.  What  are  its  compounds  with  oxygen?  298.  Characterize 
these  compounds.  (1.)  The  oxyd;  (2.)  Selenious  acid. 


200  NON-METALLIC    ELEMENTS. 

without  change  of  properties.  Selenic  acid  is  formed  by 
oxydizing  selenium  with  nitrate  of  potash,  and  it  may  also  be 
formed  by  the  action  of  nitric  acid  on  selenium.  It  strongly 
resembles  sulphuric  acid  in  its  acid  properties  and  compounds. 
Both  selenious  and  selenic  acids  form  salts  with  the  alkalies 
and  bases,  every  way  similar  to  the  sulphites  and  sulphates. 

With  sulphur,  selenium  forms  a  sulphuret  which  is  found 
native  among  volcanic  products. 

8.    TELLURIUM. 

Equivalent,  64-14.     Symbol,  Te. 

299.  Tellurium  is  a  very  rare  substance,  more  analogous 
to  sulphur  in  its  chemical  relations  than  to  the  metals,  with 
which  it  is  usually  classed.  It  is  found  native  or  alloyed 
with  gold,  and  is  also  combined  with  bismuth,  silver,  &c.,  in 
several  very  rare  minerals,  as  telluric  bismuth,  graphic 
tellurium,  and  aurotellurite. 

When  pure,  it  is  a  tin-white,  brittle  substance,  with  a 
metallic  lustre,  and  a  density  of  6-26.  It  melts  at  low  red- 
ness, is  very  volatile,  and  is  a  bad  conductor  of  heat  and 
electricity.  It  burns  when  strongly  heated  in  the  air,  and 
forms  tellurous  acid,  TcOa.  Telluric  acid,  (TeO3)  can  also 
be  formed  from  tellurous  acid,  by  a  process  which  need  not 
now  be  described. 


CLASS  IV. 

9.    NITROGEN,    OR    AZOTE.* 

Equivalent,  14-06.     Symbol,  N.    Density,  -972. 

300.  Preparation  and  History. — This  gas  forms  four- 
fifths  of  the  air  we  breathe,  and  is  an  essential  constituent  of 
most  organic  substances.  It  enters  into  a  great  variety  of 
combinations. 

(3.)  Selenic  acid.  299.  What  is  tellurium?  Give  its  properties. 
What  acids  does  it  form  ?  300.  Give  the  symbol  and  equivalent  of 
nitrogen. 


*  So  called  from  a,  privative,  and  zoe,  life,  frem  its  deadly  effects. 
Nitrogen  is  from  nitrnm,  nitre,  and  gannao,  I  form. 


NITROGEN.  201 

It  is  most  easily  procured  for  purposes  of  experiment  from 
the  atmosphere,  by  withdrawing  the  oxygen  of  the  air  by 
phosphorus.  This  is  easily  done 
by  burning  some  phosphorus  in  a 
floating  capsule,  in  an  air-jar  over 
the  pneumatic  cistern.  The  strong 
affinity  of  phosphorus  for  oxygen 
enables  it  to  withdraw  every 
trace  of  this  element,  leaving  be- 
hind nitrogen  nearly  pure,  con- 
taining about  -5^  of  phosphorus 
and  the  vapors  of  phosphorus,  ^ 
with  the  snow-white  phosphoric 
acid  which  the  water  soon  absorbs.  The  first  combustion  of 
the  phosphorus  expels  a  portion  of  the  air  by  expansion  ;  but 
as  the  combustion  proceeds  the  water  rises  in  the  jar, 
showing  a  considerable  absorption.  Pure  nitrogen  is  also 
easily  obtained  from  fused  nitrate  of  ammonia  by  aid  of  a 
bit  of  zinc,  which  is  lowered  by  a  wire  passing  through  the 
cork  of  the  tubulure,  so  as  to  bring  the  zinc  into  contact  with 
the  fused  salt.  As  soon  as  the  protoxyd  of  nitrogen  begins  to 
be  set  free,  oxyd  of  zinc  is  formed,  and  nitrogen  evolved, 
NO-f  Zn=ZnO  +  N.  Other  processes  may  be  used,  such 
as  passing  air  over  cuttings  of  copper  in  a  tube  heated  to 
redness,  and  the  action  of  nitric  acid  on  lean  animal  muscle  ; 
but  the  method  first  named  will  best  suit  our  purposes. 

301.  Properties  of  Nitrogen. — Nitrogen  is  best  described 
by  saying  that  its  properties  are  entirely  negative.  It  is  a 
fixed  gas,  which  no  degree  of  cold  and  pressure  has  ever 
liquefied.  It  cannot  support  combustion,  nor  life  ;  yet  it  is 
not  poisonous,  and  kills  merely  by  exclusion  of  air.  It  has 
neither  taste  nor  smell.  It  is  a  little  lighter  than  air,  having 
a  density  of  '972.  It  does  not  combine  directly  with  any 
element,  although  by  indirect  methods  it  enters  into  powerful 
combinations  with  several.  In  the  air,  it  seems  to  act  the 
part  of  a  diluent,  and  is  not,  properly  speaking,  in  chemical 
combination  with  the  oxygen  there  present ;  the  atmosphere 
is  regarded  as  a  mixture  of  the  two  gases,  diffused  through 
each  other,  (132.) 


How  is  it  prepared  ?  301.  What  are  its  properties  ?  Does  it 
support  life  and  combustion  ?  Is  it  poisonous  ?  Does  it  directly 
combine  with  other  elements  ?  How  does  it  act  in  common  air  ? 


202  NON-METALLIC    ELEMENTS. 


1.   The  Chemical  History  of  the  Atmosphere. 

302.  We  have  already  (24)  given  a  sufficient  account  of 
the  mechanical  or  physical  properties  of  the  atmosphere  and 
the  laws  of  gases,  and  need  not  repeat  them  here.     The 
number  and  proportion  of  the  constituents  of  the  atmosphere 
are    constant,   although    their    union   is   only   mechanical. 
Repeated    analyses    have    shown    that   atmospheric   air   is 
always  formed  of  nitrogen,  oxygen,  watery  vapor,  a  little 
carbonic  acid,  traces,  perhaps,  of  carbureted  hydrogen,  and 
a  small  quantity  of  ammonia.     The  air  on  Mount  Blanc,  or 
that  taken  in  a  balloon  by  Gay  Lussac  from  21,735   feet 
above  the  earth,  has  the  same  chemical  composition  as  that 
on  the  surface,  or  at  the  bottom  of  the  deepest  mines.     The 
carbonic  acid   being  liable  to  changes  in  quantity  from  local 
causes,   is    found    to   vary    slightly.      To   the   constituents 
already  named,  we  may  add  the  aroma  of  flowers  and  other 
volatile  odors,  and  those  unknown  mysterious  agencies  which 
affect  health,  and  are  called  miasmata.     We  may  state  the 
composition  of  the  atmosphere  in  100  parts,  to  be— - 

By  weight.  By  measure. 

Nitrogen,  77  parts.  79-19 

Oxygen,  23  20-81 

100  100-00 

To  this  we  must  add  from  3  to  5  measures  of  carbonic 
acid  in  10,000  of  air;  a  variable  quantity  of  aqueous  vapor, 
and  a  trace  of  ammonia.  Nitric  acid  has  also  been  some- 
times found  in  small  quantity  in  rain-water,  formed  in  the 
air  by  the  electrical  discharges  of  thunder-clouds,  and  washed 
out  by  the  rains.  100  cubic  inches  of  dry  air  weigh  31*011 
grains. 

303.  Analysis  of  Air. — The  oxygen  of  the  air  is  ab- 
stracted by  all  substances  having  an  affinity  for  it,  with  the 
same  ease  as  if  nitrogen  were  not  present.     The  experiments 
described  in  300  are  one  mode  of  analyzing  air.     The  term 


302.  Describe  the  chemical  composition  and  properties  of  the  air. 
Do  the  proportions  vary  ?  Which  constituents  may  vary  ?  Give 
its  constitution  by  weight  and  measure.  How  much  carbonic  acid 
is  there  in  it  ?  What  do  100  cubic  inches  weigh?  303.  How  is  the 
air  analyzed  ? 


NITROGEN.  203 

eudiometry  has  been  applied  to  processes  for  determining  the 
purity  of  the  air,  from  words  signifying  "  a 
good  condition  of  the  air."  One  of  the  sim- 
plest means  of  analyzing  the  atmosphere, 
consists  in  removing  the  oxygen  by  the  slow 
combustion  of  phosphorus.  For  this  purpose 
the  arrangement  is  made,  as  in  the  annexed 
figure,  by  sustaining  a  stick  of  phosphorus  on 
a  wire  in  a  confined  portion  of  air,  contained 
in  a  graduated  glass  tube,  whose  open  end  is 
beneath  water.  A  gradual  absorption  takes 
place,  and  in  about  twenty-four  hours  the 
water  ceases 'to  rise  in  the  tube,  by 
which  we  know  that  the  phosphorus 
has  removed  all  the  oxygen.  The 
water  absorbs  the  resulting  phosphorous  acid,  and 
we  may  read  off,  by  the  graduation  on  the  tube, 
the  amount  of  gas  removed.  A  narrow-necked 
bolt-head  shows  this  result  in  a  more  striking 
manner  in  the  class-room,  the  large  volume  of  air 
in  the  ball  causing  a  very  appreciable  rise  of  water 
in  the  stem  during  the  course  of  a  lecture.  When 
speaking  of  hydrogen,  we  will  mention  another 
method  of  eudiometry.  The  agency  of  the  air  in 
combustion  and  respiration  will  also  be  explained 
under  the  appropriate  heads.  From  this  mechanical  mixture 
of  oxygen  and  nitrogen,  we  pass  to  the 

2.  Compounds  of  Oxygen  and  Nitrogen. 

304.  Nitrogen  unites  with  Oxygen,  forming  five  com- 
pounds, three  of  which  are  acids.  Their  names  and  con- 
stitution are  thus  expressed : 

Combination  by  weight. 


Protoxyd  of  nitrogen,  (nitrous  oxyd,) 

Symbol. 
NO 

Nitrogen. 
14-06 

Oxygen. 
8 

Deutoxyd  of  nitrogen,  (nitric  oxyd,) 

N02 

14-06 

16 

Hyponitrous  acid, 

N03 

14-06 

24 

Nitrous  acid, 

NO4 

14-06 

32 

Nitric  acid, 

N05 

14-06 

40 

What  is  eudiometry  ?  Give  a  simple  mode  of  illustrating  the 
analysis  of  air.  304.  Name  the  compounds  of  oxygen  with  nitrogen. 
Give  their  composition  on  the  black-board. 


204  NON-METALLIC    ELEMNETS. 

This  group  of  compounds  is  generally  considered  as  one 
of  the  most  instructive  examples  of  the  law  of  multiple  pro- 
portions (184)  in  the  whole  range  of  chemical  affinities,  and 
our  attention  is  arrested  by  the  fact,  that  the  same  elements 
which  form  our  salubrious  air,  should,  by  mere  change  of 
proportions,  unite  to  form  the  corrosive  and  deadly  acids  of 
nitrogen. 

305.  Protoxyd  of  Nitrogen,  (NO,)  Nitrous   Oxyd,  or 
Laughing  Gas. — This  gaseous  compound  of  nitrogen  is  best 

prepared  by  heating  nitrate  of  ammonia 
(NH3,  N05)  in  a  glass  flask  by  the 
aid  of  a  spirit-lamp.  The  arrangement 
is  here  shown ;  the  gas  is  given  off  at 
about  400°  to  500°,  and  is  delivered 
by  the  bent  tube  to  an  air-jar  on  the 
pneumatic  trough.  The  nitrate  of 
ammonia,  which  is  a  crystalline  white 
salt  formed  by  neuralizing  dilute 
nitric  acid  by  carbonate  of  ammonia, 
is  so  constituted  as  to  be  resolved  by 
heat  alone,  into  nitrous  oxyd  and 
water;  thus,  NH4O,  NO3,  become  by 
heat  4HO  +  2NO.  The  hydrogen  in 
the  ammonia  takes  so  much  oxygen 
from  the  nitric  acid — three  equivalents — as  is  required  to 
form  three  equivalents  of  water,  and  the  nitrogen,  both  of 
the  acid  and  ammonia,  unites  with  the  remaining  oxygen  to 
form  the  gas  in  question.  Consequently  the  equivalents  of 
these  elements  show  us  that  71  grains  of  nitrate  of  ammonia 
will  yield  44  grains  of  nitrous  oxyd  and  27  grains  of  water. 
Care  must  be  taken  not  to  heat  this  salt  too  highly,  as  it  then 
yields  nitric  oxyd  and  nitrous  acid  fumes.  If  a  red  cloud 
towards  the  close  of  the  operation  is  seen  to  rise,  the  heat 
must  be  abated. 

306.  Properties. — Nitrous  oxyd  is  a  colorless  gas,  with 
a  faint,  agreeable  odor,  and  a  sweetish  taste.     With  a  pres- 
sure of  fifty  atmospheres  at  45°  F.  it  becomes  a  clear  liquid, 
and  at  about  150°  below  zero  freezes  into  a  beautiful,  clear, 
crystalline  solid.     By  the  evaporation  of  this  solid,  a  degree 

305.  How  is  protoxyd  of  nitrogen  prepared  ?  What  caution  is 
needed  ?  306.  What  are  the  properties  of  this  gas  ?  Has  it  been 
solidified,  and  at  what  temperature  ? 


NITROGEN.  205 

of  cold  may  be  produced  far  below  that  of  the  carbonic 
acid  bath  (137)  in  vacua,  (or  lower  than  — 174°  F.)  It  evap- 
orates slowly,  and  does  not  freeze,  like  carbonic  acid,  by 
its  own  evaporation.  The  specific  gravity  of  nitrous  oxyd 
is  1-525;  100  cubic  inches  of  it  weigh  47*29  grains.  Cold 
water  absorbs  about  its  own  volume  of  this  gas.  It  cannot, 
therefore,  be  long  kept  over  water,  but  may  be  collected  in 
vessels  filled  with  warm  water  over  the  water-trough.  It 
supports  the  combustion  of  a  candle,  and  sometimes  re-lights 
its  red  wick  with  almost  the  same  promptness  as  pure 
oxygen.  Phosphorus  burns  in  it  with  great  splendor.  With 
an  equal  bulk  of  hydrogen,  it  forms  a  mixure  that  explodes 
with  violence  by  the  electric  spark  or  a  match ;  the  residue 
is  pure  nitrogen,  the  oxygen  forming  water  with  the  hydro- 
gen. 

307.  Its  most  remarkable  property,  and  that  from  which 
it  derives  the  name  of  *  laughing  gas?  is   its  intoxicating 
power  on  the  system.     For  this   purpose  it  is  breathed  when 
pure  or  diluted  with  air,  through  a  wide  tube,  connected  with 
a   silk  or  elastic-gum  bag  or  with  a  gas-holder,  and  may  be 
inhaled  and  exhaled  several  times,  until  giddiness  comes  on, 
and  a  feeling  of  joyous  or  boisterous  exhilaration.     This  is 
shown  by  a  disposition  to  laughter,  a  flow  of  vivid  ideas  and 
poetic  imagery,  and  often  by  a  strong  disposition  to  muscular 
exertion.     These  sensations  are  usually  quite  transient,  and 
pass  away  without  any  resulting  languor  or  depression.     In 
a  few  cases  dangerous  consequences  have  followed  its  use,  and 
it  should  be  employed  with  great  caution.     In  at  least  one 
case,*  at  Yale  College,  it  produced  a  permanent  restoration  of 
health  and  joyous  exhilaration  of  spirits  which  continued  for 
months.     Its  effects,  however,  in   different    individuals   are 
various. 

308.  Deutoxyd  or  Binoxyd  of  Nitrogen,  Nitric  Oxyd. — 
This   gas  is  easily  prepared  by  adding  strong  nitric  acid  to 


How  does  the  solid  gas  behave  ?  Is  this  an  absorbable  gas  ?  307. 
What  is  its  most  remarkable  property  ?  How  does  it  affect  the  sys- 
tem ?  Are  its  effects  uniform  ?  308.  How  is  binoxyd  of  nitrogen 
formed  ? 


*  In  another  case  consumptive  symptoms  resulted,  which  continued 
for  years,  although  not  eventually  fatal. 

18 


206  NON-METALLIC    ELEMENTS. 

clippings  of  sheet  copper,  contained  in  a 
bottle  arranged  with  two  tubes  like  the 
annexed  figure ;  a  little  water  is  first  put 
with  the  copper  cuttings,  and  the  nitric 
acid  poured  in  at  the  tall  funnel  tube 
until  brisk  effervescence  comes  on.  In 
this  case  the  copper  is  oxydized  by  a  part 
of  the  oxygen  of  the  acid,  and  the  oxyd 
thus  formed  is  dissolved  by  another  por- 
tion of  acid.  The  nitrogen  in  union  with 
the  two  equivalents  of  oxygen  is  given  off 
as  nitric  oxyd,  which,  not  being  absorbed 
by  water,  may  be  collected  over  the  pneu- 
matic-trough. Many  other  metals  have  the  same  action  with 
nitric  acid. 

309.  Properties. — Nitric  oxyd  is  a  transparent,  colorless 
gas,  tasteless  and  inodorous,  but  excites  a  violent  spasm  in 
the  throat  when  an  attempt  is  made  to  breathe  it.     It  has 
never  been  condensed  into  a  liquid.     Its  specific  gravity  is 
1*039,  and  100  cubic  inches  weigh  32-22  grains.     It  contains 
equal  measures  of  oxygen  and  nitrogen  uncondensed. 

A  lighted  taper  is  instantly  extinguished  when  immersed 
in  it,  but  phosphorus  previously  well  inflamed  will  burn  in  it 
with  great  splendor.  When  this  gas  comes  into  contact  with 
the  air,  deep  red  fumes  are  produced,  by  its  union  with  the 
oxygen  of  the  air  to  form  nitrous  acid.  If  to  a  tall  jar,  nearly 
filled  with  nitric  oxyd,  standing  over  the  well  of  the  cistern, 
pure  oxygen  gas  be  turned  up,  deep  blood-red  fumes  instantly 
fill  the  vessel,  much  heat  is  generated,  and  a  rapid  absorption 
results  from  the  solution  of  the  red  nitrous  acid  vapors  in  the 
water  of  the  cistern.  If  both  gases  are  pure  and  in  the  right 
proportions,  the  absorption  will  be  complete,  and  no  gas  left 
in  the  vessel.  If  purple  cabbage- water,  made  green  by  an 
alkali,  is  used  to  fill  the  air-jar,  the  acid  formed  at  once  turns 
the  vegetable  infusion  to  a  lively  red. 

310.  Hyponitrous  Acid,  (NO3.)— This  is  a  thin  mobile 
liquid,  formed  from  the  mixture  of  four  measures  of  deut- 
oxyd  of  nitrogen  with  one  measure  of  oxygen,  both  perfectly 


309.  What  are  its  properties  ?  Is  it  respirable  ?  Is  it  condensa- 
ble ?  Give  its  specific  gravity  and  its  composition  by  volume.  Does 
it  support  combustion  ?  What  is  its  action  with  oxygen  ?  What  finr* 
experiment  is  named  ?  H10.  What  is  hyponitrous  acid? 


NITROGEN. 


207 


dry,  and  exposed  after  mixture  to  a  temperature  below  zero 
of  Fahrenheit.  It  has  an  orange  red  vapor,  and  at  common 
temperatures  is  green,  but  at  zero  is  colorless.  Water  decom- 
poses it,  forming  nitric  acid  and  deutoxyd  of  nitrogen.  Its 
most  interesting  compound  is  that  formed  with  sulphurous 
acid  in  the  manufacture  of  sulphuric  acid,  (290,)  as  already 
described. 

311.  Nitrous  Acid,  (NO4.) — We  have  already  anticipated 
the  mode  of  forming  this  compound  and  its  properties  in  de- 
scribing the  deutoxyd  of  nitrogen.     Whenever  the  latter  body 
is  brought  into  contact  with  the  air,  red  nitrous  acid  fumes  are 
formed.     By  decomposing  the  nitrate  of  lead  in  an  earthen 
retort  nitrous  acid  and  oxygen  are  obtained  and  the  former 
may  be  condensed  in  a  very  cold  receiver.     In  this  state  it  is 
a  nearly  colorless  fluid,  which  becomes  yellow  and  finally  red 
as  the  temperature  rises.     It  boils  at  82°,  and  is  decomposed 
by  water,  nitric  acid  and  deutoxyd  of  nitrogen  being  formed. 

This  body,  although  considered  as  an  acid,  is  not  very 
well  characterized.  The  red  color  of  the  strong,  fuming 
nitric  acid  of  commerce,  is  due  to  the  presence  of  nitrous 
acid  dissolved  in  the  fluid. 

312.  Nitric  Acid,  Aqua  Fortis,  (NO5HO.)— This  powerful 
and  important  acid  is  bet- 
ter known  than  any  other        R 

of  the  compounds  of  nitro- 
gen. It  is  best  obtained 
by  decomposing  either  the 
nitrate  of  soda  or  of  pot- 
ash, (saltpetre,)  by  strong 
sulphuric  acid.  The  ar- 
rangement of  apparatus 
required  is  seen  in  the 
adjoining  cut.  The  re- 
tort ( R )  con-tains  the 
nitre  in  small  crystals, 
and  should  be  supported 
in  a  sand-bath  ;  or  if  the 
salt  does  not  exceed  a  pound 
or  two,  a  naked  fire  an- 

What  compound  of  it  have  we  already  described?  311.  What  is 
said  of  nitrous  acid  ?  How  can  it  be  obtained  ?  Can  it  be  mixed  with 
water  ?  312.  How  is  nitric  acid  formed  ?  Describe  the  arrangement 
of  apparatus  and  the  proportions  of  the  materials. 


208  NON-METALLIC    ELEMENTS. 

swers  very  well.  To  it  is  added  about  twice  its  weight  of  strong 
oil  of  vitriol.  The  sulphuric  acid  takes  the  place  of  the  nitric, 
forming  bisulphate  of  soda  or  potash,  and  the  strong  nitric  acid 
distils  over  to  the  receiver,  which  is  kept  cool  by  water  or  ice. 
No  luting  of  any  kind  must  be  employed  about  its  neck.  The 
retort  becomes  very  hot,  and  the  whole  operation  is  a  critical 
one.  The  dense  red  vapors  of  nitrous  acid  which  appear  in 
the  early  stage  of  the  process  disappear  entirely  after  a  time, 
and  are  again  renewed  toward  its  close.  When  the  deep 
blood-red  vapors  prevail,  and  but  little  acid  condenses  in  the 
neck  of  the  retort,  the  heat  is  remitted  and  the  receiver  dis- 
connected ;  the  bisulphate  of  potash  is  then  in  a  state  of 
quiet  fusion  and  intensely  hot,  (about  600°  F.)  When 
nearly  cold  it  may  be  gradually  dissolved  by  hot  water,  but 
the  retort  is  generally  sacrificed  in  the  operation.  The 
strongest  nitric  acid  is  produced  only  when  equal  weights  of 
sulphuric  acid  and  nitre  are  used. 

313.  Properties. — Nitric  acid  thus  obtained  is  a  highly 
colored,    red,    fuming,   and    very    corrosive   acid,   of  great 
energy.     The  color  is  due  to  nitrous  and  hyponitrous  acid, 
the  pure  nitric  acid  being  colorless,  with  a  specific  gravity 
of  1*5,  and  boiling  at  248°.     It  stains  the  skin  yellow,  and 
acts  violently  on  most  organic  matters  and   metals.     Poured 
on  powdered  recently  ignited  charcoal,  deflagration  speedily 
ensues,  and  warm  oil  of  turpentine  is  at  once  inflamed  by  it. 

314.  One  equivalent  of  water  is  essential  to  the  character 
of  nitric  acid,  (NO5 ,  HO,)  the  simple  NOS  being  an  unknown 
substance.     The  strongest  nitric  acid  has  nine  parts  of  water 
to  54  of  real   acid.     Like   sulphuric  acid,  it   has   several 
definite   combinations  with  water,  which   freeze   and   boil  at 
very  different  temperatures.     Strong  aqua  fortis   freezes  at 
about  50°  below  zero,  but  when  diluted  with  one-half  water 
it  freezes  at  — 1-|°.     The  green  hydrated  nitrous  acid  freezes 
into  a  bluish  white  solid. 

315.  It  oxydizes  other  substances  very  powerfully,  from 
the  great  amount  of  oxygen  it  contains.     It  is  the  usual 


What  changes  are  noticed  as  the  process  goes  on  ?  When  is  the 
process  arrested  ?  313.  What  are  rts  properties  ?  What  gives  it  its 
ordinary  color  ?  How  does  it  effect  the  skin,  the  metals  and  char- 
coal ?  314.  Is  the  anhydrous  nitric  acid  known  ?  What  is  the  com- 
position of  the  strongest  nitric  acid  ?  Is  it  ever  frozen,  and  at  what 
temperature  ?  315.  How  does  it  affect  other  bodies  ? 


PHOSPHORUS.  209 

solveift  of  most  of  the  metals,  when  we  would  carry  them  to 
the  condition  of  peroxyds.  In  all  such  cases,  the  binoxyd 
of  nitrogen  is  formed,  (NO2))  which  at  once  produces  red 
fumes  in  the  air.  It  forms  a  large  class  of  salts,  (nitrates,) 
all  of  which  are  soluble  in  water.  This  makes  it  difficult 
to  detect  the  presence  of  this  acid.  It  however  decolorizes 
a  solution  of  indigo  in  sulphuric  acid,  which  is  the  common 
test  for  the  presence  of  nitric  acid ;  and  with  a  drop  or  two 
of  hydrochloric  acid  it  dissolves  gold  leaf. 

10.    PHOSPHORUS. 

Equivalent,  31-38.  Symbol,  P.  Density,  1-77. 

316.  History.  —  Phosphorus  is  an  element  nowhere  seen 
free  in  nature,  but  it  exists  largely  in  the  animal  kingdom, 
combined  with  lime,  forming  bones,  and  it  is  found  also  in 
other  parts  of  the  body.     In  the  mineral  kingdom  it  exists  in 
several  well  known  forms,  particularly  in  the  mineral  called 
apatite,  which  is  a   phosphate  of  lime.     It  is  introduced  into 
the  animal  system  by  the  plants  used  as  food,  whose  ashes 
contain  a  notable  quantity  of  phosphate  of  lime.     It  was  dis- 
covered in  1669  by  Brandt,  an  alchemist  of  Hamburg,  while 
engaged   in    seeking  for  the  philosopher's  stone,  in  human 
urine.     Its  name  implies  its  most  remarkable  property,  (phos, 
light,  and  phero,  I  carry.) 

317.  Preparation. — Phosphorus  is  now  procured  in  im- 
mense quantities  from  burnt  bones,  for  the  manufacture  of 
friction  matches.     The  bones  are  calcined  until  they. are  quite 
white;  they  are  then  ground  to  a  fine  powder,  and  fifteen 
parts  of  this  are  treated  with  thirty  parts  of  water  and  ten  of 
sulphuric  acid  :  this  mixture  is  allowed  to  stand  a  day  or  two, 
and  is  then  filtered,  to  free  it  from  the  insoluble  sulphate  of 
lime,  formed  by  the  action  of  the  oil  of  vitriol  on  the  bones. 
The  clear  liquid  (which  is  a  soluble  salt  of  lime  and  phos- 
phoric acid)  is  then  evaporated  to  a  syrup,  and  a  quantity  of 
powdered    charcoal  added.     The  whole   is  then  completely 
dried  in  an  iron  vessel  and  gently  ignited.     After  this,  it  is 
introduced  into  a  stoneware  or  iron  retort,  to  which  a  wide 
tube  of  copper  is  fitted,  communicating  with  a  bottle  in  which 

316.  What  is  phosphorus  ?  When  and  by  whom  discovered  ? 
What  existence  has  it  in  nature?  317.  How  is  it  prepared?  De- 
scribe the  process  of  procuring  it. 

18* 


210  NON-METALLIC    ELEMENTS. 

is  a  little  water,  that  just  covers  the  open  end  of  the  tube ;  a 

small  tube  carries  the  gases  given  out  to  a  chimney  or  vent. 

The  retort  being  very  gradually  heated,  the  charcoal  decom- 
poses the  phosphoric  acid,  carbonic 
acid  and  carbonic  oxyd  gases  are 
evolved,  and  free  phosphorus  flows 
down  the  tube  into  the  bottle,  where  it 
is  condensed.  The  operation  is  a  criti- 
cal one,  and  often  fails  from  the  break- 
ing of  the  retort.  Splendid  flashes  of 
light  are  constantly  given  out  during 
the  operation,  from  the  escape  of  phos- 
phureted  hydrogen.  The  crude  phos- 
phorus thus  obtained  is  purified  by 
melting  under  water,  and  it  is  then  cast 
into  glass  tubes,  where  it  is  allowed  to 

cool,  forming  the  sticks  in  which  it  is  sold. 

318.  Pure  phosphorus  is   a  yellowish    semi-transparent 
solid,  which  cuts  like  wax,  is  brittle  at  32°,  and  then  shows  a 
crystalline  fracture.     It  has  a  density  of  I'll.     It  is  insolu- 
ble in  water,  but  dissolves    in  several   oils,  in  ether,  alcohol, 
and  in  sulphuret  of  carbon :  from  the  last  it  crystallizes  in 
regular  dodecahedrons,  (220.)     It  melts  at  108°  into  a  color- 
less liquid,  and  boils  at  650°,  forming  a  colorless  vapor  of  a 
density  of  4-327. 

319.  Phosphorus  is  exceedingly  inflammable,  being  easily 
set  on  fire  by  the  heat  of  the  hand,  and  great  caution  is  re- 
quired in  managing  it.     It  must  be  kept  under  water,  to  which 
alcohol  enough  may  be  added  to  prevent  its  freezing  in  winter. 
If  exposed  to  the  "air,  it  wastes  slowly  away,  forming  phos- 
phorous acid,  and  in  the  dark  it  is  seen  to  be  luminous.     The 
vapor  which  then  comes  from  it,  has  a  strong  garlic  odor, 
which  does  not  belong  either  to  the  pure  phosphorus  or  its 
acid  compounds.     A  little  olefiant  gas,  the  vapor  of  ether,  or 
any  essential  oil,  will  entirely  arrest  the  slow  oxydation  of 
phosphorus  in  air.     The  presence  of  nitrogen  or  hydrogen 
seems  to  be  essential  to  this  operation,  as  in  pure  oxygen, 
phosphorus  does  not  form  phosphorous  acid  at  common  tem- 


318.  What  is  its  usual  condition  ?  In  what  is  it  soluble  ?  How  is 
its  density  when  solid  and  in  vapor  ?  319.  What  of  its  inflamma- 
bility ?  How  is  it  kept  ?  How  does  air  affect  it  ?  What  substances 
arrest  its  slow  combustion  ?  How  does  it  burn  in  oxygen  ? 


PHOSPHORUS.  211 

peratures.  It  burns  in  pure  oxygen  gas  with  great  splendor, 
forming  one  of  the  most  brilliant  experiments  in  chemistry. 
For  this  purpose  it  is  suspended  in  a  metallic  spoon,  in  a  dry 
globe,  filled  with  oxygen  by  displacement  of  air,  as  already 
described. 

1.  Compounds  of  Phosphorus  with  Oxygen. 

320.  The  compounds  of  phosphorus  with  oxygen  are  four 
in  number,  and  may  be  understood  from  the  following  list. 

Composition  by  Weight. 

Symbol.  Phosphorus.  Oxygen. 

Oxyd  of  phosphorus,               P2O  62-76 

Hypophosphorous  acid,           PO  31-38  8 

Phosphorous  acid,                     P03  31-38  24 

Phosphoric  acid,                       P05  31-38  40 

321.  Oxyd  of  phosphorus  is  formed  when  a  stream  of 
oxygen  gas  is  allowed  to  flow  from  a  tube  upon  phosphorus 
under  warm  water.     The  phosphorus  burns  under  water  and 
forms  a  brick-red  powder,  which  is  the  oxyd  in  question,  with 
much  unburnt  phosphorus.     This  oxyd  is  also  formed  when 
phosphorus  is  kept  for  a  long  time  under  water ;  the  sticks 
then  become  coated  with  the  red  oxyd.     By  heat,  this  oxyd 
is  decomposed  into  phosphorous  and  phosphoric  acids. 

322.  Hypophosphorous  acid  is  very  little  known,  and  we 
need  not  describe  its  mode  of  formation.     Its  salts  are  all  sol- 
uble in  water,  and  it  is  a  powerful  deoxydizing  agent. 

323.  Phosphorous  Acid. — When  some  sticks  of  phospho- 
rus are  placed  in  a  funnel,  and  its  mouth  covered,  a  delicate 
stream  of  white  vapor  is  seen  to  descend  from  the  lower  end 
of  the   tube,  which    may    be   collected  in  a  tall    foot-glass. 
These  vapors  are  phosphorous  acid,  formed  from  the  slow 
combustion  of  the  phosphorus  by  the  oxygen   of  the  air.     It 
is  also  formed  when  phosphorus  is  burnt  in  a  very  limited 
supply  of  oxygen  gas.     In  both  cases  it  soon   takes  another 
dose  of  oxygen  from  the  air,  and  becomes  a  mixture  of  phos- 
phorous and  phosphoric  acids. 

When  first  made,  phosphorous  acid  is  a  dry  white  powder, 
having  a  very  strong  affinity  for  water,  which  it  absorbs  togethei 

320.  Name  the  compounds  of  phosphorus  with  oxygen,  and  give  the 
formulas?  321.  Describe  the  oxyd,  its  formation  and  properties. 
How  does  heat  affect  it  ?  322.*  What  of  hypophosphorous  acid  ?  323. 
How  is  phosphorous  acid  formed  ?  What  are  its  properties  ? 


212  NON-METALLIC    ELEMENTS. 

with  oxygen  from  the  air,  and  gradually  becomes  phosphoric 
acid.  Its  solution  is  sour,  and  it  forms  well  determined  salts, 
(phosphites.) 

324.  Phosphoric   acid   is    formed    when    phosphorus   is 
burned   in  a  copious  supply  of  dry  air,  as  in  the  experiment 
for  obtaining  nitrogen,  (300,)  or  that  of  phosphorus  in  dry 
oxygen,  (319.)     When  wanted  in  large  quantity,  it  is  prepared 
from  the  ashes  of  bones  treated  with  sulphuric  acid,  as  already 
described.     This  solution  is  first  freed  from  lime  and  magne- 
sia, and  is  then  evaporated  to  dryncss  and   ignited,  when  the 
sulphuric  acid    is    driven  off  and    phosphoric  acid  remains 
behind  melted,  and  solidifies  on  cooling  into  a  colorless  glass, 
which  is  then  called  glacial  phosphoric  acid.     Phosphoric 
acid  is  also  formed  by  the  action  of  very  strong  nitric  acid  on 
phosphorus  ;  but  the  operation  is  a  dangerous  one,  and  should 
be  attempted  only  on  very  small  quantities  of  phosphorus,  and 
with  extreme  caution. 

325.  Phosphoric  acid  is  a  powerful  acid,  having  an  in- 
tensely sour  taste,  and  all  the  attributes  belonging  to  an  acid. 
It  has,  when  dry,  a  very  strong  affinity  for  water,  and  unites 
with    it   almost   explosively,  forming,  according  to  circum- 
stances, three  distinct  compounds,  or  phosphates  of  water, 
whose  constitution  is  as  follows  : 

Monobasic  phosphate  of  water,  or  metaphosphoric  acid,  HO-f-PQv 
Bibasic  phosphate  of  water,  or  pyrophosphoric  acid,  2HO-f-P05. 
Tribasic  phosphate  of  water,  or  common  phosphoric  acid,  3HO  +  P05. 

Each  of  these  three  phosphates  of  water  is  the  source  of 
a  distinct  series  of  salts  with  bases.  The  class  of  salts  most 
generally  known  is  that  formed  from  the  last  phosphate  of 
water,  or  the  tribasic  phosphates.  The  reader  can  consult 
Dr.  Graham's  Elements  of  Chemistry  for  a  fuller  account  of 
this  subject,  which  our  limits  prevent  our  giving  in  more 
detail. 

2.  Compounds  of  Phosphorus,  with  Members  of  the 
II.  Class. 

326.  (1.)  Chlorids  of  Phosphorus. — Of  these  there  are 
two,  the  perchlorid,  (PC15,)  and  sesquichlorid,  (PCI3.)     The 


324.  How  is  phosphoric  acid  formed?  How  from  bones?  325. 
Describe  its  properties.  How  does  water  affect  it  ?  Give  its  com- 
pounds with  water.  Which  is  common  phosphoric  acid  ? 


PHOSPHORUS.  213 

first  is  formed  when  phosphorus  is  introduced  into  a  jar  of 
dry  chlorine,  where  it  inflames  and  lines  the  sides  of  the 
vessel  with  a  white  matter,  which  is  the  perchlorid  of  phos- 
phorus. This  compound  is.very  unstable,  and  when  put  in 
water  both  it  and  the  water  suffer  decomposition,  and  hydro- 
chloric and  phosphoric  acids  result. 

327.  (2.)  Bromids  of  Phosphorus. — Two  of  these  com- 
pounds are  also  known,  and   are  easily  formed   by  mingling 
small   quantities  of  the  elements  in  a  flask  filled  with  dry 
carbonic  acid  gas ;  they  immediately  react  on   each  other, 
evolving  heat  and  light,  and  form  the  protobromid  of  phospho- 
rus, (PBr3,)  which  is  a  brown  fluid,  easily  decomposed  by 
water ;  and  the  perbomid  of  phosphorus,  (PBr5,)  which  is 
a  volatile  yellowish  white  solid,  that  sublimes  on   the  sides 
of  the  flask  and   is  easily  fused   by  gentle  heat  into  a  red 
fluid.     It   is    decomposed    by   water    into    phosphoric    and 
hydrobromic  acids. 

328.  (3.)  lodids  of  Phosphorus. — These  elements  com- 
bine in  three  proportions,  forming  protiodid  of  phosphorus, 
(PI,)   sesquiodid  of   phosphorus  (PI3))  and  the  periodid  of 
phosphorus,  (PI5.)     The  union  of  these  elements  is  accom- 
plished with  energy  by  simple  contact  in  a  dry  state.     Their 
compounds  are  not  important. 

329.  (4.)    Sulphuret   of  Phosphorus. —  Sulphur   unites 
with    phosphorus  with  prodigious  violence,   frequently  with 
a  dangerous  explosion,  and  more  than  30  or  40  grains  of  the 
latter  cannot  be  safely  put  with  the  sulphur.     Seleniuret  of 
phosphorus  is  formed  in  the  same  manner  as  the  last,  and  is 
similar  to  it  in  all  its  properties. 


CLASS  V.  THE  CARBON  GROUP. 

11.    CARBON. 

Equivalent,  6.   Symbol,  C.   Specific  gravity  in  vapor,  Q'4t2l. 
Solid  in  the  diamond,  3-52. 

330.    History. — Charcoal   and   mineral  coal,   which   are 
the  two  common  forms  of  carbon,  have  been  known   from 


326.  Name  the  chlorids  of  phosphorus.  327.  How  many  bromids 
of  phosphorus  are  there  ?  How  are  they  formed  ?  328.  How  many 
iodids  of  phosphorus,  and  how  formed  ?  329.  What  is  said  of  the 
union  of  sulphur  and  phosphorus  ?  What  of  its  seleniuret  ? 


214. 


NON-METALLIC    ELEMENTS. 


the  remotest  times  of  history.  Its  great  importance  in  the 
daily  wants  of  society,  makes  it  one  of  the  most  interesting 
of  the  elementary  bodies,  and  our  interest  in  it  is  not  dimin- 
ished from  the  fact  that  the  charcoal  and  mineral  coal  which 
we  use  as  fuel,  and  the  black  lead  of  our  pencils,  are 
essentially  the  same  thing  with  that  rare  and  costly  gem,  the 
diamond.  The  three  distinct  and  very  dissimilar  forms  of 
existence  which  this  element  assumes,  give  us  one  of  the 
best  examples  known  of  the  allotropism  (264)  of  bodies.  We 
will  very  briefly  mention  the  principal  characters  of  the  three 
forms  of  carbon — (1,)  the  diamond,  (2,)  graphite  or  plumbago, 
(4,)  mineral  coal  and  charcoal. 

331.  The  diamond  is  pure  carbon  crystallized.  It  takes 
the  forms  of  the  regular  system,  or  first  crystalline  class, 
(220,)  of  which  the  annexed  figures  are  some  of  its  common 
modifications.  Its  crystalline  faces  are  often  curved,  as  in 


the  second  figure.  The  diamond  is  the  hardest  of  all  known 
substances,  and  can  be  scratched  or  cut  only  by  its  own  dust. 
The  solid  angles  of  this  mineral,  formed  by  the  union  of  curved 
planes,  are  much  used,  when  properly  set,  for  cutting  glass, 
which  is  done  with  great  ease  and  precision.  It  has  a  specific 
gravity  of  3-52,  and  the  highest  value  of  any  kind  of  treasure. 
The  most  esteemed  diamonds  are  colorless,  and  of  an  inde- 
scribable brilliancy  ;  this  gem  has  also  a  peculiar  lustre  known 
as  the  *  adamantine  lustre.'  They  are  often  slightly  colored, 
of  a  yellowish,  rose,  blue,  or  green,  and  even  black  tint. 
The  largest  known  diamond  belongs  to  the  Great  Mogul,  and 
when  found  weighed  2769-3  grains,  or  nearly  six  ounces  :  it 
has  the  form  and  size  of  half  a  hen's  egg.  The  most  highly 
valued  diamond  in  the  world  is  called  the  Pitt  diamond,  and 
was  sold  to  the  Duke  of  Orleans  for  £130,000.  It  weighs  less 
than  an  ounce.  This  was  the  gem  which  Napoleon  mounted  in 


330.  Give  the  equivalent  and  density  of  carbon.  What  is  here 
said  of  carbon  ?  What  three  forms  of  carbon  are  named  ?  331.  What 
is  the  diamond?  What  forms  does  it  occur  under  ?  Describe  it  as 
noticed  in  the  text.  What  is  the  native  source  of  the  diamond  ? 


CARBON.  215 

the  hilt  of  his  Sword  of  State.  The  diamond  is  usually  found 
in  the  loose  sands  of  rivers,  and  is  generally  accompanied  by 
gold  and  platinum.  Its  native  rock  is  supposed  to  be  a  pecu- 
liar flexible  kind  of  sandstone,  called  itacolumite ;  and  it 
is  sometimes  found  loosely  imbedded  in  a  ferruginous  conglo- 
merate in  Brazil.  A  few  diamonds  have  been  found  in  the 
United  States. 

332.  From  its  high  refractive  power  (56)  the  diamond  is 
supposed  to  be  of  vegetable  origin.     The  sun's  light  seems 
to  be  absorbed  by  the  diamond,  for  it  phosphoresces  most 
beautifully  for  some  time  in  a  dark  place,  after  it  has  been 
exposed  to  the  sun.     It  is  a  non-conductor  of  heat  and  elec- 
tricity, and  is  very  unalterable  by  any  chemical  means.     It 
is   infusible,  and   not   attacked   by  acids  or  alkalies.     But 
heated   to  redness  in  the  air,  it  is  totally  consumed,  and   the 
sole  product  of  its  combustion   is  carbonic  acid  gas,  which 
alone  is  sufficient  proof  that  diamond  is  pure  carbon. 

333.  (2.)  Graphite  or  Plumbago. — This  form  of  carbon 
is  sometimes  improperly  called  "  black  lead"  but  it  does  not 
contain  a  trace  of  lead  in  its  composition,  and  bears  no  re- 
semblance to  it,  except  that  both   have   been   used  to   mark 
upon  paper. 

This  peculiar  mineral  is  found  in  the  most  ancient  rocks, 
as  well  as  with  those  of  a  more  modern  era.  It  is  also  fre- 
quently found  in  company  with  coal,  and  is  sometimes  formed 
artificially,  as  in  the  fusion  of  cast  iron.  It  almost  always 
contains  a  trace,  and  sometimes  several  per  cent,  of  iron, 
which  is  however  foreign  to  it;  otherwise  it  is  pure  carbon. 
It  is  very  much  used  for  making  pencils,  and  the  coarser 
sorts  are  manufactured  into  very  useful  and  refractory  melt- 
ing pots.  The  most  valued  plumbago  for  the  finest  drawing 
pencils,  has  been  brought  chiefly  from  the  Borrowdale  mine 
in  Cumberland,  England  ;  but  it  is  a  common  mineral  in  this 
country,  as,  for  instance,  at  Sturbridge  in  Massachusetts,  and 
many  other  places.  It  is  sometimes  found  crystallized  in  flat 
six-sided  prisms,  a  form  altogether  incompatible  with  that  of 
the  diamond.  It  is  soft,  flexible,  and  easily  cut ;  feels  greasy 

332.  What  origin  has  the  diamond  been  supposed  to  have,  and 
why  ?  What  are  its  relations  to  heat,  light,  and  electricity  ?  How 
affected  by  chemical  means?  What  does  affect  it?  333.  What  is 
plumbago  ?  How  found  ?  What  use  is  made  of  it  ?  How  does  it 
crystallize  ?  What  are  its  physical  properties?  How  does  intense 
heat  affect  it  ? 


£16  NON-METALLIC    ELEMENTS. 

and  marks  paper.  It  is  quite  incombustible  by  all  ordinary 
means,  but  burns  in  oxygen  gas,  forming  only  carbonic  acid 
gas,  and  leaving  a  red  ash  of  oxyd  of  iron. 

334.  (3.)    Coal.  —  The   vast   beds  of    mineral    carbon, 
known  to  us  as  anthracite,   bituminous   coal,   brown   coal, 
and  lignite,  are  all  of  them  nearly  pure  carbon.     Of  the  first 
two  of  these,  no  country  has  such  abundant  and  excellent 
supplies    as    the    United    States.     These    accumulations    of 
fuel  are  the  remains  of  the  ancient  vegetation  of  the  planet, 
which,  long  anterior  to  the  creation  of  man,  a  bountiful  Pro- 
vidence laid  away  in  the  bowels  of  the  earth  for  his  future 
use.     Bituminous  coal  differs  from  anthra'cite  only  in  having 
a  quantity  of  bituminous  matter  united  with  it,  which  in  the 
anthracite  has  been  driven  off  by  heat  and  pressure. 

335.  Charcoal  from  wood  is  the  carbonized  skeleton  of 
the  woody  fibre  which   is    found   in   all    plants.     The    best 
charcoal  is  made  by  heating  sticks  of  wood   in  tight  iron 
vessels,  without  contact  of  air,  until   all  gases  and  vapors 
cease  to  be  given  off.     A   great  quantity  of  acetic  acid,  tar, 
and  oily  matters,  with  water,  are  given  out,  and  a  jetty  black, 
brittle,  hard  charcoal  is  left  behind,  which  is  a  perfect  copy 
of  the  form  of  the  origin.il  wood.     It  is  a  non-conductor  of 
heat,  but  conducts  electricity  almost  as  well  as  a  metal.     It 
is  a  very  unchangeable  substance,  insoluble  in  water,  acids, 
or  alkalies,  suffers  little  change  from   long  exposure  to  air 
and  moisture,  and  does  not  yield  to  the  most  intense  heat  to 
which  it  can  be  subjected. 

336.  Charcoal  has  the  property  of  absorbing  gases  to  a 
most  remarkable  degree,  at  common  temperatures.     A  frag- 
ment of  recently  heated  charcoal,  of  a  convenient  size  to  be 
introduced  under  a  small  air-jar  over  the  mercurial  cistern, 
will  soon  take   up  many  times   its  own  volume  of  air,  as 
will  appear  by  the  rise  of  the  mercury  in  the  air-jar.     In 
this  case  it  absorbs  more  oxygen  than  nitrogen,  the  residual 
air  having  only  eight  per  cent,  of  oxygen  in  it.     On  heating, 
it  again   parts  with  the  gas  it  has  absorbed.     The  power  of 
absorption  seems  to  depend  entirely  on  the  natural  elasticity 
of  the  gas,  and  not  at  all  on  its  affinity  for  carbon.     Those 

334.  What  is  coal  ?  How  does  anthracite  differ  from  bituminous 
coal  ?  335.  What  is  charcoal  ?  How  is  the  best  made  ?  What 
are  its  powers  of  ronduction  ?  Is  it  a  changeable  substance  ?  336. 
What  is  said  of  its  power  of  absorbing  gases  ?  What  gases  are  most 
absorbed  by  it  ? 


CARBON.  217 

gases  that  are  most  easily  reduced  to  a  fluid  condition  by  cold 
and  pressure,  are  most  abundantly  absorbed  by  charcoal. 
Charcoal  from  hard  wood  with  fine  pores  has  this  property  in 
the  highest  degree.  Thus  charcoal  from  box-wood  freshly 
prepared,  will  absorb  of  ammoniacal  gas  90  times  its  own 
volume  ;  of  muriatic  acid  gas  85  times  ;  of  sulphureted  hy- 
drogen 81  times ;  of  nitrous  oxyd  40  times  ;  of  carbonic  acid 
32  times ;  of  oxygen  9*25  times ;  of  nitrogen  1*5  times ;  and 
of  hydrogen  1'75  times  its  own  volume. 

337.  Charcoal  also  has  the  power  of  absorbing  the  bad 
odors  and  coloring  principles  of  most  animal  and  vegetable 
substances.     Tainted  meat  is  made  sweet  by  burying  it  in 
powdered  charcoal,  and  foul  water  is  purified  by  being  strain- 
ed through  it.     The  highly  colored  sugar  syrups  are  com- 
pletely decolorized  by  being  passed  through  sacks  of  animal 
charcoal,  (bone  black,)   prepared  by  igniting  bones.     It  also 
precipitates  bitter  principles,  resins,  and  astringent  substances 
from   solution.     Common   ale  or  porter  becomes   not   only 
colorless,  but  also  in  a  good  degree   deprived   of  its  bitter 
principles,  by  being  heated  with  and  filtered  through  animal 
charcoal.     This   property  is  lost  by  use,  and  regained    by 
heating  it  afresh.     Its   power  of  absorption    seems   similar 
to  that  possessed  by  spongy  platinum,  (212.)     Hydrogen,  in 
small   quantity,  is  very  obstinately  retained  in  the  pores  of 
charcoal,  and  water  is  consequently  always  produced  from 
the  combustion  of  carbon  in  pure  oxygen  gas.     Carbon  has 
a  greater  affinity  for  oxygen  at  high  temperatures  than  any 
other  known  substance,  and  for  this  reason  it  is  useful  in 
reducing  oxyds  of  iron  and  other  oxyds  to  the  metallic  state. 

1.  Compounds  of  Carbon  with  Oxygen. 

338.  Carbon  unites  with  oxygen  in  two  proportions,  to 
form  carbonic  oxyd  and  carbonic  acid,  whose  composition  is 
thus  expressed : 

Composition  by  weight. 


Symbol.  Carbon.  Oxygen. 

Carbonic  oxyd,  CO  6  8 

Carbonic  acid,  C02  6  16 


What  rule  regulates  this  ?  Mention  some  instances  of  the  amount 
of  absorption.  337.  How  does  it  affect  bad  odors  and  vegetable 
colors  ?  What  else  does  it  also  remove  ?  To  what  is  this  analogous  ? 
What  is  said  of  its  affinity  for  oxygen  ?  338.  Name  the  compounds 
of  carbon  with  oxygen  and  their  composition. 
19 


218 


NON-METALLIC    ELEMENTS. 


339.  Carbonic  Acid.  (CO2.) — History. — This  is  the  sole 
product  of  the  combustion  of  the  diamond  or  any  pure  car- 
bon in  the  air,  or  oxygen  gas.     It  was  first  recognised  and 
described   by  Dr.   Black,  in   1757,  under  the  name  of  fxed 
air.     This  philosopher    proved    that  limestone   and  magne- 
sian  rocks  contained  a  large  quantity  of  this  gas  in  a  state  of 
solid  combination  with  the  earths,  and  also  that  it  was  freely 
given  out  in  the  processes  of  fermentation,  respiration,  and 
combustion. 

340.  Preparation. — Carbonic  acid  is  easily  procured  by 
treating   any  carbonate  with   a    dilute  acid.     Carbonate   of 
lime,  in  the  form  of  marble  powder,  is  usually  employed  for 
this  purpose ;  it  is  put  with  a  little  water'into  a  wide-mouth- 
ed bottle,  (ft,)  (like  that  used  in  308 ;)  sulphuric  or  hydro- 
chloric acid  is  turn- 
ed   in    at    the    tube 
funnel,  when  the  gas 
is  set  free  with  effer- 
vescence,   and    es- 
capes   through    the 
bent  tube.     If  it    is 
wished  to  have  the 
gas  dry,  it  is  passed 
over  dry  chlorid  of 
calcium  in  the  hori- 
zontal tube  t,  which 
completely  removes 

every  trace  of  moisture  from  it.  Its  weight  enables  us  to 
collect  it  in  dry  bottles  (a)  by  displacement  of  air,  as  in  the 
case  of  chlorine,  (260.)  No  heat  is  required,  and  the  acid  is 
added  in  small  successive  portions,  the  gas  being  freely  evol- 
ved at  each  addition.  If  the  gas  is  not  required  dry,  the  long 
chlorid  of  calcium  tube  may  be  dispensed  with.  When  ob- 
tained by  the  action  of  monohydrated  nitric  acid  on  carbonate 
of  ammonia,  the  carbonic  acid  evolved  retains  a  white  cloudy 
appearance,  even  after  passing  through  water,  which  renders 
it  visible,  a  point  of  some  importance  in  experiments  with 
this  gas. 

This  gas  can  also  be  collected  over  the  pneumatic  trough, 
not  being  absorbed  by  water  so  rapidly  but  that  it  may  be 
thus  managed  well  enough  for  experimental  purposes. 


339.  Give  the  history  of  carbonic  acid.     310.  How  is  it  prepared  ? 
Ho*v  is  it  dried  ?     Ho\v  may  it  be  colbcted  ? 


CARBON.  219 

341.  Properties.  —  At    the    common    temperature    and 
pressure,  carbonic  acid  is  a  colorless,  transparent  gas,  with 
a  pungent  and  rather  pleasant  taste  and  odor.     At  a  tempe- 
rature of  32°,  and  a  pressure  of  30  to  36  atmospheres,  it  is 
condensed  into  a  clear  limpid   liquid,  not  as  heavy  as  water, 
which  freezes  by  its  own  evaporation  into  a  white,  snow-like 
substance.     We  have  already  described  (137)  the  apparatus 
and  process  by  which  this  interesting  experiment  is  performed. 
Carbonic  acid  is  about  once  and  a  half  as  heavy  as  common 
air,  having  a  specific  gravity  of  1*524  ;  and  100  cubic  inches, 
therefore,  weigh  47*26  grains. 

342.  Cold  water  recently  boiled  absorbs  about  its  own 
volume  of  carbonic  acid   gas,  but  with  pressure   much  more 
will  be  taken  up,  in  quantity  exactly  proportioned  to  the 
pressure  exerted.     The  solution  has  a  pleasant  acid  taste,  and 
temporarily  reddens  blue  litmus  paper.     The  '  soda  water,' 
so  much  used  as  a  beverage,  is  usually  only  water  strongly 
impregnated  with  carbonic  acid,  the  soda  being  generally 
omitted  in  its  preparation.     The  effervescence  of  this,  as  well 
as  of  small  beer  and  sparkling  wines,  is  due  to  the  escape  of 
this  gas.     Natural  waters  have  usually  more  or  less  of  this 
gas  dissolved  in  them ;  and  some   mineral   springs,  like  the 
Saratoga  and  Ballston  springs,  and  the  Seltzer  water,  are 
highly  charged  with  carbonic  acid. 

343.  Carbonic   acid    instantly   extinguishes   a    burning 
taper  lowered   into   it,  even  when    mingled    with  twice  or 
three  times  its  bulk  of  air.     Fresh   lime-water  agitated  with 
this    gas,   rapidly  absorbs  it,  becoming  at   the    same   time 
milky,  from  the  production  of  the  insoluble  carbonate  of 
lime.     In  this  way  the  presence  of  carbonic  acid  is  easily 
detected,  and  this  gas  distinguished  from  nitrogen. 

344.  Death  follows  the  inspiration  of  carbonie  acid, 
even  when   largely  diluted   with  air.     It  kills   by  a  specific 
poisonous  influence  on  the  system  resembling  some  narcotics, 
and  is  unlike  nitrogen  (291)  in  this  particular,  which   kills 
only   by  exclusion   of  air,  as  waiter  drowns.     Instances  of 
death  from  sleeping  in  a  close  room  where  a  charcoal  fire  is 

341.  What  are  the  properties  of  carbonic  acid  ?  At  what  tempe- 
rature and  pressure  does  it  solidify  ?  What  is  its  gravity  ?  342. 
How  much  of  it  does  water  absorb  ?  What  is  said  of  the  solution  ? 
Ts  it  found  in  natural  waters  ?  343.  How  does  it  affect  combustion  ? 
What  test  is  there  for  it?  344.  How  does  it  affect  life  when 
breathed  ?  Is  it  poisonous  ? 


220  NON-METALLIC    ELEMENTS. 

burning,  and  from  descending  into  wells  which  contain  car- 
bonic acid,  are  lamentably  frequent.  The  latter  accident 
may  always  be  avoided  by  taking  the  obvious  precaution  to 
lower  a  burning  candle  into  the  well  before  going  into  it, 
when  if  the  candle  burns,  all  may  be  considered  sale,  but  its 
being  extinguished  is  certain  evidence  that  the  well  is  unsafe. 
Wells  containing  carbonic  acid  may  often  be  freed  from  it 
by  lowering  a  pan  of  recently  heated  charcoal  into  the  well, 
which  will  soon  absorb  thirty-five  times  its  bulk  of  this  gas, 
(336,)  thus  removing  the  evil. 

345.  Numerous  natural  sources  evolve  large  quantities  of 
carbonic  acid,  particularly  in  volcanic  districts.     It  abounds 
also,  in  common  with   gases  to  be  mentioned   hereafter,  in 
coal   mines;   it  is  produced   abundantly  by  those  explosions, 
which  are  so  often  fatal   in  the  mines,  and   kills  by  its  poi- 
sonous influences  those  who  may  esoape  the  explosion.     The 
Grotto  del  Cane,  in  Italy,  (dog's  grotto,)  is  a  noted  instance 
of  the  natural  occurrence  of  this  gas. 

It  is  always  present  in  the  air,  (302,)  being  given  off  by 
the  respiration  of  all  animals,  and  besides  the  other  sources 
already  named,  is  an  invariable  product  of  all  common  cases 
of  combustion. 

All  the  carbon  which  plants  secrete  in  the  process  of  their 
developemcnt,  is  derived  either  from  the  carbonic  acid  of  the 
atmosphere,  which  they  decompose  by  the  aid  of  sun-light 
by  their  green  leaves,  retaining  the  carbon  and  returning  the 
pure  oxygen  to  the  air;  or  it  is  absorbed  by  their  rootlets  and 
then  decomposed  by  the  sun's  light  at  the  surface  of  the  leaf. 

346.  Carbonic  acid  is  formed  of  equal  volumes  of  its 
two  constituent  gases  condensed   into  one.     For  this  reason 
the  air  suffers  no  change  of  bulk   from   the  enormous  quan- 
tities of  this  gas  which  are  hourly  formed   and   decomposed 
on  the  earth.     This  acid  unites  with  alkaline  bases,  forming 
an  important  class  of  salts,  (the  carbonates,)  which   are  all 
decomposed   by  any  stronger  acid,  with  the  escape  of  car- 
bonic acid. 

347.  Carbonic  Oxyd,  (CO.) — Preparation. — This  gas  is 
produced  in  several  ways.     (1.)  By  passing  carbonic  acid 


How  may  these  accidents  be  avoided  ?  345.  What  natural  sources 
of  it  are  named  ?  Is  it  in  the  air  ?  Whence  do  plants  get  their 
carbon  ?  346.  Give  its  composition  by  volume.  What  class  of 
salts  does  it  form  ?  317.  How  is  carbonic  oxyd  prepared  ?  First  ? 


CARBON.     .  221 

over  fragments  of  coal  heated  to  redness  in  an  iron  tube, 
the  oxygen  gains  another  equivalent  of  carbon,  and  carbonic 
oxyd  results.  (2.)  Oxalic  acid,  (C2O3,HO-|-2HO,)  when 
treated  with  five  or  six  times  its  weight  of  strong  sulphuric 
acid,  is  decomposed,  the  acid  takes  the  water  of  the  oxalic 
acid,  and  a  gas  escapes,  which  is  formed  of  equal  measures 
of  carbonic  acid  and  carbonic  oxyd.  C2O3  yield  CO  and 
CO2.  Carbonic  acid  is  absorbed  by  standing  over  water,  or 
by  agitation  of  the  gas  with  an  alkali,  and  the  carbonic  oxyd 
is  left  pure.  (3.)  The  best  method  is  that  recommended  by 
Dr.  Fownes,  which  is  to  mingle  in  a  capacious  retort  eight 
or  ten  parts  of  sulphuric  acid  with  one  part  of  dry  finely 
powdered  yellow  prussiate  of  potash.  The  salt  is  entirely 
decomposed  by  a  gentle  heat,  yielding  an  abundant  volume 
of  pure  carbonic  oxyd. 

348.  Properties. — This  is  a  colorless,  almost  inodorous 
gas,  burning  with  a  beautiful  pale  blue  flame,  such  as  is  often 
seen  on  a  freshly  fed  coal  fire.     Its  specific  gravity  is  a  little 
less  than  that  of  air,  or  *973  ;  and  100  cubic  rhches  of  it  weigh 
30-20  grains.     It  is  not  absorbed  by  water,  does  not  render 
lime-water  milky,  and  explodes  feebly  with  oxygen.     It  is  not 
irrespirable,  but  is  even  more  poisonous  than  carbonic  acid, 
producing  a  state  of  the  system  resembling  profound  apo- 
plexy.    This  gas  is  very  largely  produced  in  the  process  of 
reducing  iron  from  its  ore  in  the  high  furnace. 

Carbonic  oxyd  is  formed  of  half  a  volume  of  oxygen  and 
one  volume  of  carbon,  or  two  volumes  of  carbon  and  one  of 
oxygen  condensed  into  two  volumes. 

349.  Carbonic  oxyd  combines  with  chlorine  and  some  other 
elementary  bodies,  forming  compounds  in  which  it  appears  to 
act  the  part  of  an  element.     Its  union  with  chlorine  is  pro- 
duced by  the  influence  of  light,  «nd  the  product  is  called  phos- 
gene gas.     This  is  a  pungent,  highly  odorous,  suffocating 
body,  possessing  acid  properties,  and  decomposed  by  water. 

2.   Compounds  of  Carbon  with  the  Chlorine  Group. 

350.  The   compounds   of   oxygen   and    carbon   already 
mentioned  are  the  most  important  which  carbon  forms  with 


Second  ?  third  ?     Which  mode  is  preferred  ?     348.  What  are  its 
properties  ?     What   is  its  density  ?     How  does   it  affect  life  ?     In 
what  art  is  it  largely   produced  ?      349.  What  compound  does   it 
form  with  chlorine  ?     What  is  its  name  ? 
19* 


222  NON-METALLIC    ELEMENTS. 

the  first  class  of  the  non-metallic  elements.     But  there  are 
certain  others  which  we  will  briefly  mention.     They  are — 

Composition  by  weight. 

Symbol.            Chlorine.  Carbon. 

Chlorid  of  carbon,                CC1                 35-41  6 

Perchlorid  of  carbon,          C2C13                106-23  12 

Dichlorid  of  carbon,            C2C1                  35-41  12 

Sulphur. 

Bisulphuret  of  carbon,          €82                  32-18  6 

351.  The  chlorids  of  carbon  are  obtained  from  the  action 
of  chlorine  on  a  peculiar  body  formerly  called  Dutch  liquid,* 
produced  from  the  union  of  chlorine,  hydrogen,  and  carbon. 
We  shall   refer  any  further  mention  of  these  compounds  to 
the  organic  chemistry. 

352.  Bisulphuret  of  carbon  is  produced  by  passing  the 
vapor  of  sulphur  over  fragments  of  recently  prepared  char- 
coal,  heated  to   redness   in  a  porcelain   tube,   which  is  so 
inclined  that  the  heavy  volatile  fluid   may  run  down  in  vapor 
and   be  condensed  in  an  ice-cold  vessel  filled   with   water. 
This  product  is  redistilled,  to  purify  it. 

353.  Properties. — Bisulphuret  of  carbon,  when  pure,  is  a 
colorless  liquid,  but  has  usually  a  yellowish  tint;   its  power 
of  refracting  light  is  very  remarkable.     It   has  a  most  dis- 
gusting odor,  and   boils  at  110°.     Its  density  is  1'27,  and  in 
vapor  2-68.     It  dissolves  sulphur,   phosphorus,   and   iodine, 
these  bodies   being  deposited   again  in  beautiful  crystals  by 
the  evaporation  of  the  sulphuret  of  carbon.     It  burns  in  the 
air  at  about  600°,  with  a  pale  blue  flame.     It  forms  an  ex- 
plosive mixture  with   oxygen,  and  a  combustible  one  with 
binoxyd  of  nitrogen.     It  dissolves  easily  in  alcohol  and  ether, 
and  is  precipitated  again  by  water. 

3.   Compounds  of  Carbon  with  Nitrogen. 

354.  Carbon  forms  an  unimportant  compound  with  phos- 
phorus, but  with  nitrogen  it  unites  to  form  one  of   the  most 
remarkable  compound   bodies  known   to  chemists.     This  is 

350.  What  other  compounds  are  named  of  carbon  with  oxygen  ? 
351.  What  are  the  chlorids  of  carbon  ?  352.  How  is  the  bisulphuret 
of  carbon  prepared  ?  353.  What  are  its  properties  ?  What  does  it 
dissolve  ?  In  what  is  it  soluble  ?  351.  What  is  cyanogen  ? 


*  From  its  being  discovered  at  Harlem,  in  Holland,  by  an  asso- 
ciation of  Dutch  chprrmts. 


SILICON.  223 

called  cynanogen,  and  is  composed  of  one  equivalent  of  nitro- 
gen and  two  of  carbon,  or  NC2 .  Although  a  compound,  it 
acts  in  all  respects  like  an  element,  entering  into  combina- 
tion with  the  same  energy  with  which  elements  unite.  Its 
production  and  properties  are  referred  to  the  organic  chem- 
istry, where  it  can  be  better  understood. 

12.    SILICON. 

Equivalent,  22-18.  Symbol,  Si.  Density  in  vapor,  (hypo- 
thetical,) 15-29. 

355.  Common  quartz,  or  rock  crystal  and  gun-jlint,  are 
very  familiar  substances ;  these  are  the  compound  of  sili- 
con and  oxygen,  known  as  silica,  or  silicic  acid.     Silicon 
is,  however,  a  substance  very  rarely  seen,  even  by  chemists, 
because  it   never  occurs  in  nature,  and   is  very  difficult   to 
prepare.     Silica,    its   compound    with    oxygen,   is,    next    to 
oxygen,   the  most  abundant,  and  one  of  the  most  important 
substances  known.     It  is  calculated  that  it  forms  one-sixth 
part  of  the  crust  of  the  globe. 

356.  Preparation  of  Silicon. — Silica  retains  its  oxygen 
so    powerfully  that   it  is  very   difficult    to   separate  it  and 
leave  the  pure  silicon.     Silicon   may  be  procured,  however, 
by  an  indirect  process,  which  is  to   decompose  the   double 
fluorid  of    silicon  and  potassium,  (2SiF3-f  3KF.)      This  is 
a  white  powder,  like  starch,  and  very  sparingly  soluble  in 
water.     To  decompose  this,  it  is  mixed  with  about  its  own 
weight  of   the  metal  potassium  cut  in 

small  pieces,  and  put  in  a  test  tube  of 
hard  glass,  which  is  then  heated  over  a 
lamp.  As  soon  as  the  tube  is  heated 
on  the  bottom  to  redness,  a  vivid  ignition 
is  seen  to  take  place,  and  to  spread 
through  the  whole  mass.  The  residue 
after  this  ignition,  when  cool,  is  treated 
with  water,  which  dissolves  all  the  fluo- 
rid of  potassium  that  has  been  formed  in  the  process,  leaving 
behind  the  silicon.  Thus  the  ('2SiF3  +  3KF)  acted  on  by 
6K  give  9KF  and  2Si. 

How  does  it  act  ?  Where  do  we  consider  it  ?  355.  Of  what  is 
silicon  the  basis  ?  Is  it  a  natural  substance  ?  How  abundant  is 
silica?  356.  How  is  silicon  prepared  ?  Give  the  reaction. 


224  NON-METALLIC    ELEMENTS. 

357.  Properties. — Silicon  is  a  dark  nut-brown  powder, 
without    metallic  lustre,  and  a  non-conductor  of   electricity. 
Heated  in  air  or  oxygen  it  burns,  forming  silica.     If  heated 
in  a  close  vessel,  it  shrinks  and   becomes   more  dense.     Be- 
fore ignition  it  is  soluble  in  hydrofluoric  acid,  but  after  this 
it  is  insoluble,  and  is  incombustible  in  the  air  or  oxygen  gas. 
It  seems  then  to  resemble  the  graphite   variety  of  carbon. 
These  two  diverse  conditions  of  silicon  are  probably  con- 
nected with  the  two    states  in  which    silica   occurs.     This 
element  has  been  often  called  a  metal,  and. named  accordingly 
silicium ;  but  if  power  to  conduct  electricity,  and  the  posses- 
sion of  a  metallic  lustre,  are  attributes  of  a  metal,  silicon  has 
no  claim  to  be  so  classed.     Its  real  affinities  are  more  with 
carbon. 

Compounds  of  Silicon. 

358.  The  known  compounds  of  silicon  are  not  numerous; 
those  mentioned  in  this  section  are — 

Composition. 


Symbol.  Silicon.  Oxygen. 

Silicic  acid,  (silica,)  SiO3  22-18  24 

Chlorine. 
Chlorid  of  silicon,  SiCl3  22-18  106-23 

Bromine. 
Bromid  of  silicon,  SiBr  22-18  234-78 

Fluorid  of  silicon,  SiF3  22-18  56-10 ' 

Sulphur. 
Sulphuret  of  silicon,  SiS3  (probably)  22-18  66-27 

The  similarity  of  composition  in  these  bodies  is  a  remark- 
able circumstance,  as  will  be  seen  at  a  glance  by  inspecting 
their  formulas. 

359.  Silicic  acid  or  Silica,  (SiO3.) — This  oxyd  of  sili- 
con exists  abundantly  in  nature  in  the  form  of  rock  crystal, 
agate,  common  uncrystallized  quartz,  silicious  sand,  &c. ;  it 
also  enters  largely  into  combination  with  other  substances  to 
form  the  rock  masses  of  the  globe.  It  is  a  very  hard  sub- 
stance, easily  scratching  glass,  and  is  difficult  to  reduce  to  a 
powder;  its  specific  gravity  is  2-66.  It  is  infusibb  alone, 

357.  What  are  its  properties  ?  How  does  heat  affect  it  ?  What 
two  states  of  it  are  noticed  ?  To  what  are  these  analogous  ?  Why 
not  consider  it  a  metal  ?  358.  What  compounds  of  silicon  are 
named  ?  359.  What  is  silicic  acid  ?  Give  its  properties. 


SILICON.  225 

except  by  the  power  of  the  compound  blowpipe.  It  dissolves 
with  effervescence  in  fused  carbonate  of  'soda  or  potash  ;  the 
effervescence  being  due  to  the  escape  of  carbonic  acid  from 
the  alkali,  which  is  replaced  by  the  silicic  acid.  No  acid 
(except  the  hydrofluoric)  has  any  effect  on  silica.  When  in 
its  finest  state  of  division  it  is  still  harsh  and  gritty  to  the 
touch  or  between  the  teeth. 

360.  Silica  is  known  in  two  very  unlike  conditions — its 
insoluble  or  common  condition,  and  its  soluble  or  hydrous 
state.     When  silica  is  dissolved  in  a  fused  alkali,  and  then 
again  this  silicated  alkali  in  a  strong  acid,  as  the  hydrochloric, 
we  obtain  on  evaporating  the  solution  to  a  small  bulk,  a  trem- 
ulous gelatinous  mass,  which  is  soluble  silica.     If  an  excess 
of  alkali  is  used,  the  silicate  formed  is  soluble  in  water,  and  is 
sometimes  called  the  liquor  of  flints.     If  this  soluble  silica  is 
dried,  it  is  again  reduced  to  its  insoluble  condition.     Most 
natural  waters  contain  some  small  portion  of  soluble  silica ; 
it  has  been  often  seen  in  this  state  in  mines ;  and  on  breaking 
open  silicious  pebbles,  the  central  parts  are  sometimes  semi- 
fluid and  gelatinous.     The  hot  waters  of  the  great  geysers  in 
Iceland,  and  of  other  hot  springs,  also  dissolve  large  quanti- 
ties of   silica,  probably  aided  by  alkaline  matter.     Agates, 
chalcedony,  cornelian,  &c.  have  been  deposited  from  the  sol- 
uble state.     It  is  in  this  condition,  no  doubt,  that  silica  enters 
the  substance  of  many  vegetables,  as,  for  instance,  the  reeds 
and  grasses,  which  have  often  a  thick  crust  of  silica  on  their 
bark.     It  also  produces  most  beautiful  petrifactions  of  natu- 
ral objects,  as  corals,  shells,  arid  many  vegetables,  completely 
replacing  the  organic  matters,  and  turning  them  into  solid 
quartz  or  elegant  chalcedonies  and  agates. 

361.  The  uses  of  silica  in  the  arts  are  very  important. 
It  is  the  basis  of  all  glass,  being  fused  with  alkalies  to  form 
this   useful  and  beautiful  substance,  (see  glass  and  pottery,) 
and  also  of  porcelain  and  all  kinds  of   potters'  ware.     In 
chemistry  its  uses  are  chiefly  confined  to  certain  analytical 
operations  of  no  importance  to  our  present  object. 

362.  It  is  called  an  acid,  from  the  power  it  has  of  acting 
the  part  of  a  powerful  acid  at  high  temperatures.     At  ordi- 


What  dissolves  it  ?  360.  What  two  unlike  conditions  of  silica  are 
named  ?  How  is  the  soluble  condition  produced  ?  How  do  we  find 
it  in  nature  ?  What  function  does  it  discharge  ?  361.  What  are  the 
uses  of  silica  ?  362.  Why  is  it  called  an  acid  ? 


226  NON-METALLIC  ELEMENTS. 

nary  temperatures  its  insolubility  renders  its  acid  properties 
insensible  to  all  our  usual  tests  lor  acids.  When  by  a  suffi- 
cient temperature  it  is  rendered  soluble,  we  sec  its  acid  char- 
acter very  distinctly  in  the  ease  with  which  it  completely 
saturates  the  most  powerful  alkalies. 

363.  Chlorid  of  silicon  is  formed  by  passing  a  current  of 
dry  chlorine  gas  over  silicon  heated  to  redness  in  a  tube  of 
porcelain  or  glass  ;  or,  more  simply,  by  employing,  in  place  of 
silicon,    the    finely  powdered    silica,    mixed    with    powdered 
charcoal  in  the  same  tube,  and  treated  in  the  same  manner. 
The  carbon  takes  the  oxygen  of  the  silica  at  the  high  temper- 
ature, and  the  chlorine  unites  with  the  silicon  to  form  a  very 
volatile   chlorid    of  silicon,   which    is    condensed  in  a    cold 
receiver,  while  the  excess  of  chlorine,  and  the  carbonic  oxyd 
formed  in  the  process,  escape  as  gases.     The  chlorid  of  sili- 
con is  a  colorless  liquid,  denser  than  water,  and  boils  at  124°. 
Water  decomposes  it,  forming  hydrochloric  acid  and  silica. 

There  is  a  bromid  of  silicon  possessing  the  same  properties 
and  formed  in  an  exactly  similar  manner. 

364.  Fluorid  of  silicon,  (fluosilicic  acid.) — The  affinity 
existing  between  fluorine  and  silicon  is  one  of  the  strongest 
known  to  chemists.     We  have  already  mentioned  this  while 
speaking  (280)  of  fluorine.     Fluorid  of  silicon  may  be  pro- 
cured   by   heating  a  mixture  of  powdered    flour-spar    and 
quartz  with  strong  oil  of  vitriol : 

Fluor-spar.     Silica.        Sul.  arid.          Sul.  lime.       Water.     Fluorid  silicon. 
3CaF  -f  SiO3 -f  3(SO3,HO)  =  3(CaO,  SO3)  +  3HO  +  SiF3. 

Being  rapidly  absorbed  by  water,  it  must  be  collected  over 
mercury.  It  forms  dense  white  vapors  with  the  moisture  of 
the  air,  as  soon  as  it  comes  in  contact  with  it. 

365.  Properties. — This  is  a«  dense,  colorless  gas,  having 
a  specific  gravity  of  about  3-60,  air  being  1  :  it   has   lately 
been  rendered  fluid  by  Dr.  Faraday,  with  a  cold  of  160°  be- 
low zero,  and  a  pressure  of  about  nine  atmospheres.     When 
this  gas  is  passed  into  a  vessel  of  water,  it  is  decomposed, 
each   bubble  becomes    incrusted  in  a  shell  or  sack  of  pure 
silica,  and  retains  its  form   more  or  less  as  it  rises  through 


Why  are  its  acid  properties  concealed  ?  363.  How  is  chlorid  of 
silicon  formed  ?  What  are  its  properties  ?  364.  How  is  fluorid  of 
silicon  formed  ?  Give  the  reaction  on  the  black-board.  Is  it  ab- 
sorbed ?  36/5.  Give  its  properties.  How  does  it  behave  in  contact 
with  water  ? 


BORON.  227 

the  water,  which  soon  becomes  milky,  from  the  quantity  of 
finely  divided  silica  suspended  in  it.  Meanwhile  the  water 
becomes  a  solution  of  hydrofluosilicic  acid,  2(SiF3) -f- 3HF, 
which  is  formed  from  the  decomposition  of  one-third  of  the 
fiuorid  of  silicon,  giving  silica  and  hydrofluoric  acid,  which 
last  unites  with  the  remaining  fluorid  of  silicon,  and  dissolves 
in  water.  The  fluosilicic  acid  gas  should  not  be  passed 
directly  into  water,  but  the  tube  should  dip  under  the  surface 
of  a  portion  of  mercury  in  the  bottom  of  the  bottle  holding 
the  water ;  if  this  precaution  is  neglected,  the  open  end  of 
the  tube  soon  becomes  plugged  up  with  silica,  and  the  gas 
bottle  may  burst.  This  acid  solution  is  decomposed  by  heat. 
It  forms  almost  insoluble  salts  (double  fluorids)  vfith  the 
metals  potassium  and  sodium,  and  hence  is  of  value  in 
separating  these  substances  from  their  solutions. 

366.  Silicon,  when   heated  with  sulphur,   unites  with  it, 
forming  a  sulphuret,   which  is  a  white   earthy    compound, 
(SiS3.)     It  is  decomposed  by  water  into  silica  and  sulphureted 
hydrogen. 

13.    BORON. 

Equivalent,  10' 90.     Symbol,  B.     Density  in  vapor,  (hypo- 
thetical,) -751. 

367.  The  only  compound  of  boron  commonly  known  is 
borax,   a   salt    much   used   in  the   arts.     Boracic   acid    (its 
compound  with  oxygen)   is  found  in   the  waters  of  certain 
lagoons  or  lakes  in  Tuscany,  from  which  large  quantities  of 
it  are  introduced  to  commerce.     This  acid,  accompanied  by 
sulphur  and  selenium,  is  also  sublimed   among  the  volcanic 
products  of  the  volcanoes  at  the  Lipari  islands,  and  in  other 
similar  places. 

368.  Boron  is  prepared  by  a  process  very  similar  to  that 
which   produces  silicon.     The  double  fluorid  of   boron  and 
potassium  being  treated  with  potassium  in  an  iron   vessel 
heated  to  redness,  gives  us  KF,  BF3+ 3K=4KF  +  B.     The 
boron    remains   as   a   dark   olive-green   powder,   after    the 
soluble  fluorid  has  been  dissolved  out  by  water.     Heated  in 


What  reaction  takes  place?  What  caution  is  required?  366. 
What  is  the  sulphuret  of  silicon  ?  367.  Give  the  equivalent  and 
symbol  for  boron.  How  is  it  found  associated  in  nature  ?  368.  How 
is  boron  prepared  ? 


228  NON-METALLIC    ELEMENTS. 

air  to  about  600°,  it  burns  brilliantly,  producing  boracic  acid. 
It  does  not  conduct  electricity,  is  insoluble  in  water  and  all 
other  neutral  fluids.  Heated  out  of  contact  with  air,  it  suf- 
fers no  change.  It  is  easy  to  see  how  similar  these  charac- 
ters are  to  those  possessed  by  carbon  and  silicon. 

Compounds  of  Boron. 

369.  The  compounds  of  boron  mentioned  under  this  head 
are 

Composition  by  weight. 

Symbol.  Boron.  Oxygen. 

BoAcic  acid,  B03  10-90  24 

Chlorine. 
Chlorid  of  boron,  BC13  10-90         106-23 

Fluorine. 
Fluorid  of  boron,  BF13  10-90  56-10 

Sulphur. 
Sulphuret  of  boron,         683  10-90          48-27 

370.  Boracic  acid,  as  just  mentioned,  is  found  native,  and 
is  also  produced,  when  boron  is  burnt  in  oxygen  or  common 
air.     It  is  easily  prepared   by  decomposing  common   borax 
(borate  of  soda)  dissolved  in  about  4  parts  of  hot  water,  with 
one-third  its  weight  of  sulphuric  acid.     Sulphate  of  soda  is 
formed  and  boracic  acid  set  free,  which,  being  nearly  insolu- 
ble in  cold  water,  is  deposited  in  pearly  scales  as  the  solution 
cools.     When  quite  cold,  the  supernatant  fluid  is  poured  off, 
and   the  white  scales  washed   with  cold  water.     This   is   a 
hydrate  of   boracic  acid,  BO3  +  3HO.     Half  this  water  of 
crystallization    is   expelled   at  212° ;  when  it  melts  into  a 
fusible  glass,  which  is  brittle  and  clear  when  cold.     Boracic 
acid  is  little  soluble  in  cold,  but  readily  in  hot  water ;  and  its 
watery  solution   cannot   be   evaporated   without   the   steam 
carrying  away  a  large  portion  of  the  acid.     The  glassy  acid 
is,  however,  quite  fixed,  even  at  a  red  heat.     Alcohol  dis- 
solves boracic  acid,  and  the  solution   burns  with  a  peculiar 
and  quile  characteristic  green  color.     Its  acid   powers  are 
feeble ;    its   salts   (borates)   being  all  decomposed  even  by 
weak  acids.     It  turns  blue   litmus  to  a  port-wine  color,  but 

What  are  its  properties  ?  To  what  is  it  likened?  369.  Name  the 
compounds  of  boron  in  this  section.  370.  How  is  boracic  acid 
formed  ?  What  are  its  properties  ?  What  is  the  glacial  acid  ?  Can 
the  watery  solution  be  evaporated  ?  What  is  its  proper  solvent  ?  What 
characteristic  property  has  it  '(  What  of  its  acid  characters  ? 


HYDROGEN.  229 

does  not  redden  it,  and  affects  yellow  turmeric  paper  like  an 
alkali,  turning  it  brown. 

371.  It  is  used  in  the  arts  to  promote  the  fusion  of  other 
bodies,  which  it  does  in  a  remarkable  degree,  by  the  fusi- 
bility of  all  its  salts.     It  is  also  much  used  as  a  flux  in  blow- 
pipe operations  and  in  the  laboratory. 

372.  Chlorid  of  boron  is  formed  in  the  same  manner  as 
the  chlorid  of  silicon,  boracic  acid  being  used  in  place  of 
silica.     It  is  a  dense,  colorless,  transparent  gas   at  ordinary 
temperatures,  having  a  specific  gravity  of  4-09 ;  and  by  cold 
and  pressure  it  may  be  reduced  to  a  fluid.     It  has  a  pungent, 
acid  smell,  and  forms  thick  vapors  in  the  air.     It  is  absorbed 
by  water,  and  is  collected  over  mercury. 

373.  Fluorid  of  boron. — The  same  process   by  which 
fluorid  of  silicon  is  prepared  yields  fluorid  of  boron,  by  sub- 
stituting boracic  for  silicic  acid.     The  gas   is  similar,  and 
has  a  density  of  2'362,  and   an  avidity   for  water   which 
causes  it  to  form  dense  fumes  in  the  air.     It  is  decomposed 
by  water,  hydrofluoboric  acid  being  formed,  which   is  per- 
fectly analogous  to  hydrofluosilicic  acid. 

374.  The  sulphuret  of  boron  is  a  white  powder  formed 
from  the  combustion  of  boron  in  the  vapor  of  sulphur,  and  is 
quite  similar  to  the  sulphuret  of  silicon.     It  is  decomposed 
by    water,    boracic   acid   and    sulphureted    hydrogen    being 
formed. 

CLASS  VI. 

HYDROGEN. 

Equivalent,  I.  Symbol,  H.  Density,  0-069. 

375.  History. — Hydrogen  was  first  described   as   a  dis- 
tinct gas  by  the  English  chemist  Cavendish,  in  1766,  and 
was   called    by   him    inflammable  air.     It    had    previously 
been   confounded   with   other  combustible  gases,  several  of 
which  had  been  long  known.     Hydrogen   exists   abundantly 
in  nature  as  a  constituent  of  water,  whence  its  name,  (193.) 
It  is  also  a  constituent  of   nearly  all   animal  and  vegetable 

371.  Of  what  use  is  boracic  acid  ?  372.  What  is  said  of  the 
chlorid  of  boron  ?  373.  What  of  the  fluorid  ?  To  what  are  it  and  the 
chlorid  similar  ?  374.  What  of  the  sulphuret  of  boron  ?  375.  Give 
the  equivalent,  symbol,  and  density  of  hydrogen.  When  and  by 
whom  was  hydrogen  discovered  ?  In  what  manner  does  it  exist  in 
nature  > 
20 


230  NON-METALLIC    ELEMENTS. 

substances,  in  which  it  exists  in  such  proportions  to  oxygen 
as  to  form  water  during  the  combustion  of  these  bodies." 

376.  Preparation. — This  gas  is  best  prepared  for  use 
by  the  action  of  dilute  sulphuric  acid  on  zinc  or  iron. 
Zinc  is  usually  preferred  as  yielding  a  purer  gas.  The  acid 
is  diluted  with  four  or  five  times  its  bulk  of  water,  and  the 


operation  may  be  conducted  in  a  glass  retort,  or  more 
conveniently  in  the  small  way  by  using  a  gas  bottle  (a)  con- 
taining the  zinc  in  small  fragments,  to  which  the  dilute  acid 
is  turned  through  the  tube  funnel,  (b.)  The  shorter  tube 
(f)  with  a  flexible  joint  conveys  the  gas  to  the  air-jar,  (e,) 
standing  in  the  cistern,  (g.)  No  heat  is  required  in  this 
operation.  An  ounce  of  zinc  yields  615  cubic  inches  of 
hydrogen  gas.  When  it  is  required  in  large  quantity,  a 
leaden  pot  or  stone  jar,  properly  fitted,  and  holding  a  gallon 
or  more,  is  used  to  contain  the  requisite  charge  of  materials, 
and  the  gas  is  stored  for  use  in  a  gas-holder  such  as  has 
already  been  described  and  figured,  ( 258. )  Zinc  is 
readily  granulated,  by  being  turned  when  melted,  into  cold 
water. 

377.  Properties. — Hydrogen  when  pure  is  a  clear  color- 
less gas,  which  no  amount  of  cold  and  pressure  yet  obtained, 
has  reduced  to  a  liquid  form.  It  refracts  light  very  power- 
fully, and  has  the  highest  capacity  for  heat  of  any  known 
gas.  It  is  inodorous  and  tasteless,  and  may  be  breathed 
without  inconvenience  when  mingled  with  a  large  quantity  of 
common  air.  It  cannot,  however,  support  respiration  alone, 
and  an  animal  plunged  in  it  soon  dies  of  suffocation.  Water 

376.  How  is  it  prepared  ?  Describe  the  process.  377.  Give  the 
properties  of  hydrogen  mentioned  in  this  section.  Is  it  poisonous  ? 


HYDROGEN.  231 

absorbs  only  about  one  and  a  half  per  cent,  of  its  bulk  of 
pure  hydrogen  gas.  The  voice  of  a  person  who  has  breathed 
it  acquires  for  a  time  a  peculiar  shrill  squeak. 

378.  Hydrogen  is  the  lightest  of  all  known  forms  of  mat- 
ter, being  sixteen   times  lighter  than  oxygen,  and   fourteen 
times  and  a  half  as  light  as  common  air.     100  cubic  inches 
of   it  weigh  only  2-14  grains.     Soap-bubbles  blown  with   it 
from  a  bladder  rise  rapidly  in  the  air ;  and  it  is  usually  em- 
ployed to  fill  balloons,  being  the  lightest  gas  which  can  be  pro- 
duced, and  the  cheapest,  if  we  except  common  coal  gas.     A 
turkey's  crop,  well  cleansed,  makes  a  good  balloon  on  a  small 
scale,  for  the  class-room,  and  very  beautiful   small  balloons 
(from   1^  to  5  feet  diameter)  are  prepared  in  Paris   of  gold- 
beaters' skin.     Hydrogen  is  so  named  from  the  fact  that  it 
forms  water  by  its  union  with  oxygen.  (Hudor,  water,  and 
gennao,  to  form.) 

379.  Hydrogen   is   the  most  attenuated  form  of  matter 
with  which  we  are  acquainted.     We  have  reason  to  suppose 
the   molecules  of  this  body  to  be  smaller  than  those  of  any 
other  now  known  to  us.     Dr.  Faraday,  in  his  attempts  to 
liquefy  this  gas,  found  that  it  would  leak  and  escape  through 
an  apparatus  which  was  quite  tight  to  other  gases.     Thus 
hydrogen  leaked  freely  with  a  pressure  of  27  or 

28  atmospheres,  through  stop-cocks  that  were 
perfectly  tight  with  nitrogen  at  50  or  60  atmos- 
pheres. This  extreme  tenuity,  together  with  the 
remarkable  law  of  diffusion  of  gases  already 
explained,  (132,)  renders  it  unsafe  to  keep  this 
gas  in  any  but  perfectly  tight  vessels.  A  small 
crack  in  a  bell  jar,  quite  too  narrow  to  leak  with 
water,  will  soon  render  the  hydrogen  with  which 
it  may  be  filled  explosive.  The  superiority  in 
diffusive  power  which  hydrogen  has  over  com- 
mon air,  is  well  seen  in  what  is  called  Mr.  Gra- 
ham's  diffusion  tube,  of  which  a  figure  is  annexed. 
A  glass  tube  11  or  12  inches  long  and  of  convenient  size, 
has  a  tight  plug  of  dry  plaster  of  Paris  at  the  upper  end,  and 

How  does  it  affect  the  voice  ?  378.  What  is  said  of  its  density  ? 
What  do  100  cubic  inches  weigh  ?  For  what  purpose  is  it  used  ? 
Give  the  meaning  of  the  word  hydrogen.  379.  What  is  said  of  the 
molecules  of  hydrogen  ?  What  was  the  result  of  Dr.  Faraday's 
experiments  on  it  ?  How  is  its  tenuity  evident  from  the  law  of 
diffusion  ?  Explain  the  diffusion  tube. 


232  NON-METALLIC    ELEMENTS. 

being  filled  with  dry  hydrogen  by  displacement  of  air,  and  its 
lower  end  put  into  a  glass  of  water,  the  hydrogen  escapes  so 
rapidly  through  the  plaster  plug,  that  the  water  is  seen  to  rise 
in  the  tube,  so  as  in  a  few  moments  to  replace  nearly  all  the 
hydrogen,  and  the  remaining  portion  of  gas  is  found  to  be 
explosive.  Hydrogen  also  enters  into  combination  in  a  smaller 
proportionate  weight  than  any  known  body,  (188,)  and  con- 
sequently has  been  chosen  as  the  unit  of  the  scale  of  equiva- 
lents. Sounds  are  propagated  in  hydrogen  with  but  little 
more  power  than  in  a  vacuum. 

380.  Hydrogen   is   a   most  eminently  combustible  gas, 
taking    fire  from   a  lighted  taper,  which  is  instantly  extin- 
guished  by  being  plunged    into   the  gas.     It  burns    with    a 
very  faint  light  and  a  bluish  white  flame.     Its  extreme  levity 
requires  this  experiment  to  be  performed   in   an  inverted  ves- 
sel like  the  annexed  figure.     A  dry  bottle  with  its    mouth 

downward  is  well  suited  to  collect  this  gas  by  dis- 
placement of  air,  as  the  heavier  gases  are  collected 
(260)  by  the  reverse  position.  When  lighted,  the 
gas  burns  quietly  at  the  mouth  of  the  bottle  ;  and 
the  extinguished  taper  may  be  relighted  by  the 
flame  at  the  mouth.  If  the  bottle  is  suddenly  re- 
versed after  the  gas  has  burned  awhile,  the  remain- 
ing gas  being  mixed  with  common  air,  will  burn 
explosively  with  a  single  flash.  Three  of  the  most 
remarkable  properties  of  hydrogen  arc  thus  shown 
by  one  experiment,  viz :  its  extreme  levity,  its 
combustibility,  and  its  explosive  union  with  oxygen. 
If  this  gas  is  incautiously  mingled  with  common 
air,  or  much  more  with  pure  oxygen,  a  severe  explosion 
results  when  the  mixture  is  fired.  The  eyes  or  limbs  of  inex- 
perienced operators  have  thus  too  often  paid  the  forfeit  by  the 
explosion  of  gas  vessels.  Particular  caution  is  required  not 
to  collect  any  gas  from  the  vessel  in  which  it  is  generated 
until  all  the  common  air  is  expelled,  as  well  from  the  genera- 
tor, as  from  the  receiving-vessel  or  gas-holder. 

381.  Pure  hydrogen  is  not  yielded  by  the  methods  before 

Why  was  hydrogen  chosen  as  the  unit  of  the  scale  of  equivalents  ? 
How  are  sounds  propagated  by  it?  380.  What  of  the  combustibility 
of  hydrogen  ?  How  does  it  burn  ?  What  three  remarkable  proper- 
ties of  hydrogen  may  be  shown  in  one  experiment,  and  how  ?  What 
caution  is  given  about  collecting  gases  ?  381.  Why  is  hydrogen  not 
pure  when  obtained  by  the  mode  described  ? 


HYDROGEN. 


233 


described.  The  gas, 
when  obtained  from  iron, 
has  always  a  peculiar 
and  offensive  odor,  due 
in  a  measure  to  the  pre- 
sence of  a  volatile  oil, 
formed  by  the  gas  with 
the  carbon  always  found 
in  iron.  That  yielded 
by  the  use  of  zinc  is  also 
somewhat  impure,  both 
having  a  portior  of  the  metals  dissolved  in  the  gas,  which 
tinge  the  flame.  Traces  of  sulphureted  hydrogen  and  car- 
bonic acid  are  akn  usually  found  in  hydrogen,  being  formed 
from  the  impurities  in  the  metals  by  which  the  gas  is  evolved. 
Some  of  these  impurities,  and  particularly  the  vapor  of  the 
acid,  which  is  carried  over  mechanically,  are  removed  by 
passing  the  gas  through  a  second  bottle  containing  an  alkaline 
solution,  in  water  or  alcohol.  It  is  generally  advisable  to 
pass  gases  through  a  portion  of  water  or  some  other  fluid 
which  will  remove  from  them  their  impurities. 

382.  Water  is  the  sole  product  of  the  combustion  of 
hydrogen  in  common  air,  or  in  oxygen  gas. 
The  combustion  of  a  jet  of  hydrogen,  and 
the  production  of  water  from  this  combus- 
tion, and  certain  musical  tones,  are  all  neatly 
shown  by  an  arrangement  like  the  annexed 
figure.  The  gas  is  generated  in  the  bottle  a, 
and  a  perforated  cork  at  the  mouth  has  a 
small  glass  tube,  from  the  narrow  end  of 
which  the  stream  of  hydrogen  is  lighted. 
An  open  glass  tube  (&)  held  over  this  flame, 
is  at  once  bedewed  by  the  water  produced  in 
the  combustion,  and  a  musical  tone  is  gene- 
rally given  out,  by  the  interruption  which 
the  flame  suffers  from  the  rapid  current  of 
air,  ascending  through  the  tube,  which  causes  it  to 
flicker,  and  being  momentaril)  extinguished,  there  occur 
a  series  of  little  explosions.  The  pitch  of  the  note  pro- 


With  what  is  it  contaminated  ?     How  may  it  be  purified  ?     382. 
What  is  the  product  when  hydrogen  is  burnt  in  air  or  oxygen  ?     De- 
scribe the  philosopher's  lamp  and  the  musical  tones  with  hydrogen. 
20* 


234  NON-METALLIC    ELEiMENTS. 

duced  depends  on  the  length  and  size  of  the  glass  tube, 
and  the  size  of  the  jet  of  hydrogen,  which  should  be  small. 
If  the  jet  is  fitted  to  the  gas-holder,  we  can  modulate  the  tone 
by  turning  the  key  of  the  stop-cock  regulating  the  supply  of 
gas.  The  little  gas  bottle  (a)  with  a  small  jet  is  often  called 
"  the  philosopher's  lamp." 

1.  Nature  of  Hydrogen. 

383.  The  real  nature  of  Hydrogen  was  for  a  long  time 
not  well  understood.  It  was  associated,  with  oxygen  and 
chlorine,  because  it  was  supposed  to  bear  the  same  relations 
to  hydrochloric  acid  that  oxygen  bears  to  sulphuric  and 
chloric  acids.  Dr.  Kane  insisted  on  the  highly  electro-posi- 
tive nature  of  hydrogen  ;  and,  to  prove  to  the  satisfaction  of 
chemists  that  this  gaseous  body  was  in  reality  more  nearly 
allied  to  iron,  zinc,  copper,  and  manganese,  than  to  any  other 
class  of  bodies,  he  showed  that  the  compounds  of  hydro- 
gen with  oxygen,  chlorine,  iodine,  sulphur,  &c.,  were  almost 
universally  electro-positive  in  combination,  and  possessed 
basic  characters,  derived  from  the  pre-eminent  electro-positive 
energies  of  hydrogen  itself.  It  is  now  the  belief  of  nearly 
all  philosophical  chemists,  that  hydrogen  is  most  closely 
allied  to  the  metals,  particularly  to  zinc  and  copper ;  that  the 
chlorids,  iodids  and  fluorids  of  hydrogen,  although  they  pos- 
sess the  characters  which  we  assign  to  acids,  resemble  in 
many. respects  the  chlorids,  iodids,  &c.,  of  the  same  metals; 
that  in  fact  hydrogen  is  a  metal,  exceedingly  volatile,  proba- 
bly standing  in  that  respect  in  the  same  relation  to  mercury 
that  mercury  does  to  platinum,  but  still  possessed  of  all  truly 
chemical  peculiarities  of  the  metallic  state,  and  no  more 
deprived  of  the  common-place  qualities  of  lustre,  hardness,  or 
brilliancy,  than  is  the  mercurial  atmosphere  which  fills  the 
apparently  empty  space  in  the  barometer  tube.*  The  vapor 
of  mercury,  and  of  other  volatile  metals,  is  like  hydrogen  a 
non-conductor  of  heat  and  electricity ;  but  we  cannot  on  this 
account  deny  their  metallic  character.  We  must  not  forget 
that  hydrogen  may  yet,  by  sufficient  cold  and  pressure,  bo 

383.  What  is  said  of  the  nature  of  hydrogen?  To  what  is  it 
compared  ?  What  is  the  present  opinion  of  chemists  about  hydrogen  ? 
What  analogous  cases  have  we  in  the  volatile  metals  ? 

*  Dr.  Kane's  Elements,  page  409,  English  edition. 


HYDROGEN.  235 

made  solid  or  fluid,  when  doubtless  we  shall  see  its  resem- 
blance in  physical,  as  well  as  we  now  do  in  chemical  charac- 
ters, to  the  metals.  The  propriety  of  giving  hydrogen  the 
place  in  our  classification  which  it  occupies,  will  now  be 
more  apparent  to  those  who  have  usually  seen  it  placed  next 
to  oxygen. 

2.   Compounds  of  Hydrogen  with .  Oxygen. 

384.  There  are  two  known  compounds  of  hydrogen  with 
oxygen,  viz : 

Composition  by  weight. 

Symbol.        Hydrogen.        Oxygen. 
Water,  (the  oxyd  of  hydrogen,)  HO  1 

Binoxyd  of  hydrogen,  HOz  1  16 

The  first  of  these  is  the  most  remarkable  compound  known, 
whether  we  contemplate  it  in  its  purely  chemical  relations,  or 
in  reference  to  the  wants  of  man  and  the  present  condition 
of  the  globe. 

385.  Water. — The  reader  has  already  been  made  familiar 
with  the  composition  of  water,  as  formed  by  the  union  of 
two  volumes  of  hydrogen  and  one  of  oxygen.     Frequent 
mention  has  been  made  of  it  in  the  foregoing  pages  of  this 
work,  as  an  illustration  of  the  principles  of  combination  and 
decomposition.     We  cannot  properly  understand  the  produc- 
tion of  hydrogen  by  any  process,  without  studying  at  the 
same  time  the  constitution  of  water.     In  examining  the  com- 
pounds of  hydrogen  and  oxygen,  as  in  all  other  chemical  in- 
vestigations, we  can  pursue  the  subject  either  analytically  or 
synthetically ;  that  is,  we  can  either  form  the  compounds 
by  the  direct  union  of  the  elements,  or  we  can  decompose 
these  compounds,  and  thus  gain  a  knowledge  of  their  consti- 
tution. 

386.  The  Decomposition  of  Water. — The  simplest  case 
of  the  decomposition  of  water  is  that  where  metallic  potas- 
sium is  employed,  which  is  directly  oxydized  by  the  water, 
hydrogen  being  evolved.     The  reaction  is  K-f  HO— KO-f  H, 
which  last  is  given  off. 

387.  The  voltaic   decomposition  of   water  has  already 
been  described,  (235,)  and  we  need  not  repeat  it  here.     It 

384.  What  are  the  compounds  of  hydrogen  and  oxygen  ?  Give  their 
composition.  385.  What  is  said  of  the  constitution  of  water  ?  How 
can  we  proceed  in  studying  the  compounds  of  hydrogen  and  oxygen  ? 
386.  What  is  the  simplest  case  of  the  decomposition  of  water  ? 


236 


NON-METALLIC    ELEMENTS. 


is,  however,  by  far  the  most  satisfactory  means  of  decom- 
position which  we  possess,  since  both 
elements  of  the  water  are  evolved  in  a 
pure  form  and  in  exact  atomic  propor- 
tions. In  fact  this  is  a  complete  ex- 
perimentum  crucis,  being  both  analysis 
and  synthesis  ;  for  we  may  so  arrange 
the  single  tube  apparatus,  that  the  mix- 
ed gases  from  the  electrolysis  of  water 
may  be  fired  by  the  ignition  of  the  wires, 
as  soon  as  a  sufficient  volume  of  the 
mixture  has  been  collected.  A  com- 
plete absorption  follows  the  explosion, 
and  the  gases  again  go  on  collecting. 
The  oxygen  which  is  dissolved  in  water 
from  the  air,  always  makes  this  experi- 
ment, when  accurately  performed,  seem 
to  show  a  very  slight  excess  in  the  oxygen. 

388.  The  decomposition  of  water  by  heat  in  the  manner 
here  figured  is  one  of  the  best  methods  of  analyzing  water, 
both  from  its  satisfactory  results,  and  its  cheapness  and  ease 
of  accomplishment.  An  iron  tube,  (as  a  gun-barrel,)  or  a 

tube  of  porcelain,  c,  is  laid 
horizontally  over  a  fire,  or 
heated  in  a  furnace  to  full 
redness.  The  tube  con- 
tains clean  turnings  of 
iron,  or  better,  a  bundle 
of  clean  iron  wire  of 
known  weight.  A  small 
retort  (a)  holding  a  little 
water  is  boiled  by  a  spirit  lamp  at  the  moment  when  the 
iron  is  at  a  full  red  heat ;  the  vapor  of  the  water  coming  into 
contact  with  the  heated  iron,  is  decomposed,  the  oxygen  is 
retained  by  the  iron,  forming  oxyd  of  iron,  and  the  hydro- 
gen is  given  off  from  the  tube,y,  which  may  be  made  to  con- 
duct it,  either  to  the  pneumatic  trough,  or  to  a  gas-holder  like 
the  one  already  figured,  (258.)  For  every  eight  grains  of 
weight  acquired  by  the  iron,  46  cubic  inches  of  hydrogen, 
weighing  one  grain,  have  been  evolved. 

387.  What  is  the  voltaic  mode  of  decomposition  ?  388.  Describe  the 
method  of  decomposing  water  by  heat.  What  is  the  reaction  in  this 
case  ?  How  much  hydrogen  do  we  get  for  eight  grains  of  gain  in  the  iron  ? 


HYDROGEN.  237 

389.  The  iron  in  this  case  is  evidently  substituted   for 
the  hydrogen,  taking  its  place  with  the  oxygen  to  form  the 
oxyd  of  iron,  while  the  hydrogen  is  set  free.     The  oxyd  of 
iron  resulting  from  this  action  is  the  same  black  oxyd  which 
the  smith  strikes  off  in  scales  under  the  hammer,  being  a 
mixture  of  protoxyd  and  peroxyd.     This  case  of  affinity  is 
an  interesting  one,  because  it  is  seemingly  reversed  when, 
under  the  same  circumstances,  we  pass  a  stream  of  hydro- 
gen  over   oxyd  of  iron,  by  means  of  which  the  iron  is 
reduced  to  the  metallic  state,  and  water  is  produced.     It  will 
be  remembered  that  we   cited   this    instance,   (211,)    while 
speaking  of  the  influence  of  quantity  of  matter  in  determin- 
ing the  nature  of  the  chemical  changes  which  might  take  place 
among  bodies. 

390.  The  decomposition  of  water  by  zinc  or  iron  in  the 
ordinary  mode  of  procuring  hydrogen  can  now  be  satisfac- 
torily explained.     As  already  stated,  dilute  sulphuric  acid  is 
added  to  fragments  of  zinc,  or  to  iron  filings,  and  hydrogen 
gas  is  given  off  abundantly  with  effervescence.     The  action 
continues  until  either  the  zinc  or  acid  is  all  consumed,  or 
until  there  is  no  longer  water  enough  to  dissolve  the  resulting 
sulphate  of  zinc.     Thus  we  take 

Zn  +  SO3+HO,  and  we  obtain  H+(SO3  +  ZnO.) 

In  other  words,  the  zinc  has  taken  the  place  before  occupied 
by  hydrogen,  while  the  oxygen  of  that  atom  of  water  has 
united  with  the  zinc,  to  form  oxyd  of  zinc.  *  The  acid  dis- 
solves this  oxyd  as  fast  as  it  is  formed,  thus  making  a  con- 
stantly renewed  surface  of  clean  metal.  The  water  serves 
to  dissolve  the  sulphate  of  zinc  as  fast  as  it  is  formed.  Zinc 


389.  What  is  the  action  of  the  iron  in  this  case  ?  What  oxyd  is 
formed  ?  390.  How  is  the  decomposition  of  water  by  zinc  explained  ? 
Give  the  reaction.  How  is  it  in  case  we  employ  hydrochloric  acid  ? 
(Note.)  What  does  the  acid  do,  and  what  the  water  ?  How  do  the 
electrical  relations  affect  this  change  ? 


*We  can  state  this  reaction  in  much  more  simple  terms,  by  em- 
ploying hydrochloric  acid  in  place  of  sulphuric  acid  :  we  have  then 

Hydrochloric  acid-}- zinc.         Hydrogen -fchlorid  of  zinc. 
HCl-fZn  and  obtain  H  +  ZnCl. 

In  this  case  there  is  no  oxydation,  for  the  same  change  is  made  when 
dry  hydrochloric  acid  is  used,  and  consequently  no  compound  con- 
taining oxygen  is  present. 


238  NON-METALLIC    ELEMENTS. 

and  iron  decompose  water  even  without  the  aid  of  an  acid, 
but  only  with  great  slowness,  and  the  action  ceases  as  soon  as 
the  metal  is  covered  by  the  coating  of  the  oxyd  thus  formed, 
which  protects  it  from  further  corrosion.  A  dilute  acid 
removes  this  coating  of  oxyd,  and  also  aids,  no  doubt,  in 
establishing  such  electrical  relations  as  to  make  the  zinc 
highly  electro-positive.  That  this  is  the  fact,  seems  quite  pro- 
bable, because  pure  zinc  is  hardly  affected  by  dilute  acids, 
and  we  have  already  noticed  the  effects  of  amalgamation 
(161,  note)  in  rendering  the  zinc  incapable  of  decomposing 
water. 

391.  It  was  formerly  said  that  the  presence  of  an  acid  in 
water  with  zinc  disposed  the  zinc  to  decompose  the  water, 
because  the  acid  was  ready  to  take  up  the  oxyd  as  soon  as 
formed.     This  was  called  a  case  of  disposing  affinity.     But 
there  can  be  no  oxyd  of  zinc  to  exert  this  influence  on  the 
acid,  until  the  water  is  decomposed ;  so  that  the  idea  that  the 
acid  disposed  the  zinc  to  decompose  the  water  is  quite  futile. 
We  find  a  much  simpler  and  more  probable  explanation  in 
the  foregoing  section. 

392.  The  recompo&ition  or  formation  of  water  from  its 
elements  may  be  effected  in  a  variety  of  ways.     A  mixture 
of  oxygen  and  hydrogen  gases  will  never  unite  under  ordi- 
nary circumstances  of  temperature,  &c. ;  but  the  passage  of 
an  electric  spark  through  them,  or  the  application  of  red-hot 
flame,  or  intensely  heated  wire,  will    produce  an  explosive 
union,  destructive  to  the  containing  vessel,  unless  the  gas  is 
in  extremely  small  quantities. 

If  this  mixture  is  made  in  exact  atomic  proportions,  and 
the  gases  are  pure,  the  result  of  the  explosion  will  be  a  com- 
plete condensation ;  but  usually  one  of  the  gases  is  in  slight 
excess. 

393.  This  explosion  may   be  safely  made  in  a  tube  of 
very  strong  glass,  holding  only  one  or  two  cubic  inches  of 
the  mixed  gases.     This  tube  is  usually  graduated  into  parts 
of  a  cubic  inch,  and  is  fitted  with  two  wires  for  the  passage 
of  the  spark,  which  come  near  to  each  other,  but  do  not 
touch.     A  gas  pistol  of  metal,  (a,)  like  the  figure,  gives  a 
perfectly  safe  method  of  performing  this  experiment,  being 


391.  What  is  said  of  disposing  affinity  ?     392.  How  is  the  recom- 
position of  water  effected  ? 


COMPOUNDS  OF  HYDROGEN.  239 

filled  with  the  mixed  gases  and  stopped  with  a  cork,  (o  ;)  a 
smart  explosion  follows  the  passage  of  the  spark,  and  the 
cork  is  forcibly  driven  out  by  the  expansion  of 
the  uniting  gases,  accompanied  by  flame. 

A  bladder  filled  with  the  mixed  gases  in 
atomic  proportions,  will  be  blown  into  shreds 
with  a  deafening  explosion,  by  the  application 
of  a  match  to  a  pin-hole  made  in  its  side.  Soap- 
bubbles  filled  from  a  bag  of  the  explosive  mixture 
will,  from  their  lightness,  rise  rapidly,  and  may 
be  exploded  by  a  match  or  candle.  In  all  these 
cases  the  sole  result  is  the  production  of  water  ;  but,  being  in 
the  form  of  vapor,  it  escapes  unseen. 

394.  The  formation  of  water  may  be  proved  by  burning 
a  jet  of  hydrogen  in  a  dry  vessel  of  oxygen,  or  even  of  com- 
mon air.     For  this  purpose  the  jet  of  the  compound  blow- 
pipe is  introduced  into  a  large   dry   globe   of   glass,    and 
the  supply  of  the  two  gases   regulated   by  the  stop-cocks. 
The  interior  of  the  globe  is  immediately  bedewed  with  the 
vapor  of  water  produced  in  the  combustion,  which  rapidly 
collects  in  drops  on  the  sides  of  the  vessel,  and  runs  down 
to  the  bottom.     No  question   in  science  has  excited  more 
inquiry  and  research,  than  the  constitution  of  water.     Re- 
peated trials,  both  analytical  and  synthetical,  often  on  a  most 
liberal  scale  and  long  continued,  have  been  made  to  prove 
it ;  and  the  uniform  result  of  the  best  experiments  has  been, 
that  8  parts  by  weight  of  oxygen  require  1  part  by  weight  of 
hydrogen  to  form  9  parts  of  water,  and  that  2  volumes  of 
hydrogen  saturate  1  volume  of  oxygen. 

395.  Hydrogen  is  frequently  employed  in  eudiometry,  or 
in  the  analysis  of  gases.     For  this  purpose  a  known  volume 
of  hydrogen  is   mingled  with  a  given  amount  of  the  gas 
to  be  analyzed,  and   the  mixture  is  exploded   by  electricity 
in  a  graduated  tube  of  glass,  or  some  other  similar  form  of 
apparatus.     The  figure  of  a  very  good  form  of  eudiometer 
invented   by    Dr.  Ure,  is    here   annexed.     It  is  a  U  tube 
of  stout  glass  ten  or  twelve  inches  long,  the  shorter  limb  of 
which  is  closed,  and  graduated  into  decimals  of  a  cubic  inch. 


393.  How  may  this  conveniently  be  done  ?  Name  some  other 
similar  experiments.  394.  How  is  the  water  produced  in  these  ex- 
periments made  manifest  ?  Describe  the  experiment.  395.  How 
is  hydrogen  used  in  eudiometry  ? 


240 


NON-METALLIC    ELEMENTS. 


Two  wires  of  platinum,  for  the  passage  of 
the  spark,  arc  fused  into  the  glass  near 
the  top.  When  it  is  to  be  used,  it  is  filled 
with  dry  mercury,  by  placing  it  horizon- 
\N  tally  in  the  mercury  trough,  and  a  conve- 
nient portion  of  the  mixture  of  the  gas  to 
be  examined  with  hydrogen  is  then  intro- 
duced. The  thumb  is  placed  over  the 
open  end,  and  by  adroit  management  all 
the  mixture  is  transferred  to  the  closed 
end  of  the  tube,  and  by  forcing  out  a 
portion  with  a  rod,  thrust  into  the  open 
end,  the  mercury  is  made  to  stand  at  the 
same  level  in  both  limbs.  These  adjust- 
ments being  made,  the  whole  bulk  of  the 
mixture  is  read  on  the  graduation,  and  while  the  thumb  is 
firmly  held  over  the  open  end  of  the  tube,  an  electrical 
spark  is  made  to  explode  the  gases.  The  air  between  the 
thumb  and  the  mercury  acts  like  a  spring  to  break  the  force 
of  the  explosion ;  and  afterwards,  on  removing  the  thumb, 
the  weight  of  the  atmosphere  forces  the  mercury  into  the 
shorter  leg,  to  supply  the  partial  vacuum  occasioned  by  the 
union  of  the  gases.  Proper  allowances  being  made  for  tem- 
perature and  pressure,  the  quantity  of  residual  gas  is  read  on 
the  graduation,  and  a  calculation  can  then  be  made  of  the 
amount  of  oxygen  present.  If  the  gas  contains  carbon, 
carbonic  acid  would  be  formed,  and  must  be  absorbed  by  an 
alkali. 

396.  The  union  of  oxygen  and  hydrogen  can  however  be 
effected  slowly  and   quietly  without  any  explosion,  or  visible 
combustion.     This  may  be  done  by  passing  the  mixed  gases 
through  a  tube  heated  below  redness,  when  combination  takes 
place,  without  explosion.     This   result  is  accomplished  at  a 
still  lower  temperature,  if  the  tube  contains  coarsely  pow- 
dered  glass  or  sand.     We  see  in  this  case  the  operation  of 
that   remarkably  power   of    surface   (212)    once   or   twice 
alluded  to  before ;    and  we  will  now  mention  a  still  more 
remarkable  instance  of  the  same  action. 

397.  Power  of  platinum  in  promoting  the  union  of  Oxy- 


Describe  lire's  eudiometer.  How  is  it  used  ?  396.  How  is  the 
quiet  union  of  hydrogen  and  oxygen  accomplished  ?  397.  How  does 
platinum  produce  this  result  ? 


COMPOUNDS    OF    HYDROGEN.  24-1 

gen  and  Hydrogen. — Professor  Dobereiner  of  Jena,  many 
years  ago,  (in  1824,)  observed  that  platinum  in  the  state  of 
fine  division,  known  as  spongy  platinum,  would  cause  an 
immediate  union  of  these  gases.  The  common  instrument 
employed  for  lighting  tapers  is  made  by  taking 
advantage  of  this  principle.  A  little  spongy  pla- 
tinum is  formed  into  a  ball,  like  the  annexed  figure, 
and  mounted  on  a  ring  of  wire  which  slips  within 
the  cup  (d)  on  the  top  of  gas-holder,  (a,  second 
fig.)  The  gas  is  generated  by  the  action  of  dilute  acid  in  the 
outer  vessel  (a)  on  a  lump  of  zinc  (z)  hang- 
ing in  the  inner  vessel,  (jf,)  and  is  let  out  at 
pleasure  by  the  cock,  (c,)  issuing  in  a  stream 
on  the  spongy  platinum.  The  latter  is  at 
once  heated  to  redness  by  the  stream  of  hy- 
drogen, which  is  condensed  within  its  pores  to 
such  a  degree  that  it  combines  with  a  portion 
of  oxygen,  always  present  in  the  sponge  by 
atmospheric  absorption.  The  union  of  these 
gases  is  always  attended  by  intense  heat,  and, 
as  a  consequence,  the  platinum  at  once  ^o\vs 
with  redness,  and  the  hydrogen  i$  ihflamed.  After  some 
time  the  sponge  loses  this  property  1o  a  certain  extent,  but  it 
is  again  restored  by  being  well  ^ignited.  When  the  spongy 
platinum  is  mixed  with  clay  and  sal-ammoniac  and  made  into 
balls,  its  effects  are  less  intense,  and  such  balls  are  often  used 
in  analysts  to  cause  t^  gradual  combination  of  gases. 

398.  Dr.  Farada^  has  sliowBv  however,  that  it  is  by  no 
means  essential  that  the  platinum  should  be  in  the  spongy 
form  in  order  to  effect  the  result.  Clean  slips  of  platinum 
foil,  and  even  of  gold  and  palladium,  can  produce  the  union 
of  hydrogen  and  oxygen.  For  this  purpose  the  platinum  is 
cleaned  in  hot  sulphuric  acid,  washed  thoroughly  with  pure 
water,  and  hung  inja  jar  of  the  mixed  gases.  Combination 
then  takes  place  so  Vapidly  as  to  cause  at  every  instant  a  sen- 
sible elevation  of  thS  water  in  the  jar.  If  the  metal  is  very 
thin,  it  sometimes  becomes  hot  enough  during  the  process  of 
combination  to  glow,  or  even  to  explode  the  gases. 


What  common  instrument  illustrates  this  ?     In   what  state  is  the 
platinum  ?     How  is  the  heat  produced  ?     398.  What  has  Dr.  Faraday 
shown  about  platinum  ?     How  is  it  cleaned  ?     What  follows  its  im- 
mersion in  the  mixed  gases  ?  » 
21 


242  NON-METALLIC    ELEMENTS. 

399.  The  same  effect  of  platinum  in  causing  combination 
is  seen  in  other  bodies  besides  oxygen  and  hydrogen.     Sev- 
eral  mixtures  of  carbon  gases  will  act  with  platinum  in  the 

same  way,  and  the  vapors  of  alcohol  or  ether 
may  be  oxydized  by  a  coil  of  platinum  wire 
hung  from  a  card  in  a  wine-glass  containing 
a  few  drops  of  either  of  these  fluids.  The 
coil  of  wire  is  heated  to  redness  in  a  lamp, 
and  while  still  hot  is  hung  in  the  glass;  it 
then  retains  its  red-hot  condition  as  long  as  any 
vapor  of  ether  or  alcohol  remains.  In  this 
case,  only  the  hydrogen  of  the  ether  or  alco- 
hol is  oxydized,  and  the  carbon  is  unaffect- 
ed ;  a  peculiar  irritating  ethereal  odor  is  given  off,  which 
affects  the  nose  and  eyes  unpleasantly.  Little  balls  of  plati- 
num sponge  suspended  over  the  wick  of  an  alcohol  lamp  will 
glow  after  the  lamp  is  extinguished.  This  is  a  common  toy 
at  the  instrument-makers. 

400.  Compound  or  oxyhydrogcn  blowpipe. — The  heat  pro- 
duced by  the  combustion  of  oxygen  and  hydrogen,  in  atomic 
proportions,  is   the   most    intense  that   can    be   obtained  by 
artificial  means.     Dr.  Hire  of  Philadelphia  was  the  first  who 
succeeded    in    forming   an    instrument  to  burn  these   gases 
together  safely,  which   Professor  Silliman  called  "  the  com- 
pound  blowpipe."     The  invention  was   afterwards  appropri- 
ated by   Dr.  Clark   in  England.     Tkj?  arrangement  of  this 
instrument   is   such,    that   the  two  gases  are  brought  from 
separate  gas-holders,  by  flexible  tubes,  so  as  to  deliver  at  the 
same  time  two  volumes  of  hydrogen,   and  one  of  oxygen 
gas,  the  hydrogen  gas  tube  terminating  in  a  hollow  cylindri- 
cal jet,  inside  of  which  passes  the  jet  of  oxygen  gas.     Thus 
arranged,  the  gases  come  in  contact  only  at  the  moment  of 
combustion,  and  all  danger  of  explosion  .is  avoided. 

The  flame  from  the  compound  blowpipe  differs  from  the 
common  flame  of  a  lamp  or  candle,  by  I  eing,  so  to  speak,  an 
entire  cone  of  ignited  aerial  matter,  instead  of  being  (like  a 
lamp  flame)  ignited  only  on  the  outside  ;  (see  flame  and  com- 
bustion.) Numerous  modifications  of  the  compound  blowpipe 


399.  What  further  case  of  surface  action  is  instanced?  400. 
What  is  the  compound  blowpipe,  and  by  whom  invented  ?  How  is 
it  arranged  ?  How  does  its  flame  differ  from  that  of  a  common 
lamp  ? 


COMPOUNDS    OF    HYDROGEN. 


243 


are  in  use,  the  most  important  of  which  we  will  barely  men- 
tion. That  most  generally  adopted,  and  the  most  safe,  is  to 
store  the  gases  in  separate  holders,  and  bring  them,  as  just 
mentioned,  by  distinct  tubes  to  a  common  jet. 

401.  Two  bags  of  gum-elastic  cloth  answer  very  well  to 
hold   the  two  gases,  and  are  fitted 

after  the  fashion  of  a  bellows,  with 
a  hinge  on  one  side.  This  is  the 
mode  usually  adopted  in  the  arrange- 
ment of  the  hydroxygen  microscope. 
The  effects  of  the  compound  blow- 
pipe may  also  be  safely  produced  by 
passing  a  stream  of  oxygen  from  a 
gas-holder  through  the  flame  of  a 
spirit-lamp,  (tr,)  as  is  seen  in  the 
annexed  figure.  The  jet  is  regula- 
ted by  the  cock,  (£,)  and  the  Tamp 
flame  supplies  the  hydrogen. 

402.  The   mixed   gases  in  atomic  proportions  are  some- 
times forced  by  a  condensing  syringe  into  a  very  strong  me- 
tallic box,  from  which  they  issue  by  their  own 

elasticity.  To  prevent  the  danger  of  an  explo- 
sion, a  contrivance  is  employed  called  "  Hcm- 
ming's  safety  tube,"  which  is  a  brass  tube  six 
or  eight  inches  long,  filled  with  fine  brass 
wire,  closely  packed,  and  having  a  conical  rod 
of  brass  forcibly  driven  into  their  centre,  by 
which  the  wires  are  very  closely  crowded 
together.  This  forms  in  fact  a  great  number 
of  small  metallic  tubes,  through  which  the  gas 
must  pass.  It  is  a  property  of  such  small 
tubes  entirely  to  arrest  the  progress  of  flame,  as 
we  shall  see  under  the  compounds  of  carbon  and 
hydrogen.  (469.)  The  jet  is  screwed  to  one  end 
of  this  tube,  and  the  other  end  is  connected 
with  the  holder  of  the  mixed  gases.  Several 
severe  explosions,  it  is  said,  have  occurred,  even  with  all 
these  precautions  ;  so  that  if  the  mixed  gases  are  used  at  all, 


401.  What  arrangements  are  adopted  for  this  instrument  ?  How 
may  oxygen  be  employed  alone  ?  402.  How  are  the  mixed  gases 
used  alone  ?  What  is  Hemming's  tube  of  safety  ? 


244  NON-METALLIC    ELEMENTS. 

it  should  be  only  in  a  bag  or  bladder,  the  bursting  of  which 
can  be  attended  with  no  danger. 

403.  The  effects  of  the  compound  blowpipe  arc  very  re- 
markable. In  the  heat  of  its  focus  the  most  refractory 
metals  and  earlhs  arc  fused,  or  dissipated  in  vapor.  Plati- 
num, which  docs  not  melt  in  the  most  intense  furnace  of  the 
arts,  here  fuses  with  the  rapidity  of  wax,  and  is  even  volatili- 
zed. By  the  adroit  management  of  the  keys,  which  a  little 
practice  soon  teaches,  we  can  either  reduce  metallic  oxyds,  or 
oxydize  substances  still  more  highly.  The  flame  of  the  mixed 
gases  falling  on  a  cylinder  of  prepared  lime,  adjusted  to  the 
focus,  produces  the  most  intense  artificial  light  known.  This 
is  sometimes  called  the  Drummond  light.  It  is  now  extensive- 
ly employed  in  distant  night  signals,  and  can  be  seen  further 
at  sea  than  any  other  light.  Much  use  is  also  made  of  it  as 
a  substitute  for  the  sun's  light  in  optical  experiments,  which  is 
a  most  important  fact  in  the  experimental  sciences.  All 
optical  results  can  be  more  conveniently  shown  by  the  oxyhy- 
drogen  light  than  by  the  sun ;  and  thus  many  instructive  ex- 
periments can  1x3  exhibited  to  an  evening  audience,  or  on  a 
dark  day.  The  galvanic  focus  alone,  among  artificial  sources 
of  light,  equals  it. 

3.  Natural  and  Chemical  History  of  Water. 

4*04.  Water  when  pure  is  a  colorless,  inodorous,  tasteless 
fluid,  which  conducts  heat  and  electricity  very  imperfectly. 
It  refracts  light  powerfully,  and  is  almost  incapable  of  com- 
pression. We  have  made  so  much  use  of  water  as  an  exam- 
ple, in  illustration  of  the  laws  of  heat,  &c.,  in  the  first  part 
of  this  volume,  that  the  reader  must  already  be  familiar  with 
many  of  its  attributes.  Its  greatest  density,  it  will  be  remem- 
bered, (86,)  is  found  to  be  at  39°-5,  or,  more  exactly,  39°-83. 
It  is  the  standard  of  comparison  (38)  for  all  densities  of  solids 
and  liquids.  In  the  form  of  ice,  its  density  is  0*92,  and  it 
freezes  at  32°.  One  imperial  gallon  of  water  weighs  70,000 
grains,  or  just  ten  pounds.  The  American  standard  gallon 
holds,  at  39°-83  Fahr.,  58,372  American  troy  grains  of  pure 


403.  What  are  the  effects  of  the  compound  blowpipe  ?  What  is 
the  Drummond  light  ?  What  use  is  made  of  it  ?  404.  Give  the  pro- 
perties of  pure  water.  Of  what  is  it  the  standard  ?  How  much 
does  the  imperial  gallon  hold  ?  How  much  the  American  ? 


COMPOUNDS    OF    HYDROGEN.  24-5 

distilled  wafer.  One  cubic  inch  at  00°  and  30  inches  baro- 
meter weighs  252-458  grains,  which  is  815  times  as  much  as 
a  like  bulk  of  atmospheric  air.  One  hundred  cubic  inches 
of  aqueous  vapor,  at  212°  and  30  inches  barometer,  weigh 
14*96  grains,  and  its  specific  gravity  is  0-6202. 

405.  Water  boils  under  ordinary  circumstances  at  212°; 
but  we  have  seen  (119)  that  its  boiling  point  was  very  much 
affected  by  the  nature  of  the  vessel.     Since  the  first  part  of 
this   volume  was  printed  we  are  lately  informed,  that  water 
may  be  heated  even  to  275°,  provided  it  be  perfectly  free  from 
air,  and  that  this  is  the  case  even  in  a  vacuum.     It  evaporates 
at  all  (129)  temperatures. 

406.  Pure  water   is   never  found  on  the  surface  of  the 
earth,  for  the  purest  natural  waters  contain  small  quanties  of 
earthy  or  saline  matters  which  they  have  dissolved  from  the 
rocks  and  soil.     Moreover,  all  good  water— that  which  is  fit 
for  the  use  of  man — has  a  considerable  quantity  of  carbonic 
acid  and  atmospheric  air  dissolved  in  it,  and  without  which  it 
would    be   flat   and    unpalatable.      Many    mineral    springs, 
besides  the  saline  matters  they  hold  in  solution,  are  highly 
charged  with   sulphureted   hydrogen,  carbonic  acid  gas,  and 
other  gases  derived  from  decomposition,  in  the  strata  through 
which  they  pass. 

407.  Pure  icater   can  be  procured  only  by  distillation, 
and  it  is  a  substance  of  such   indispensable  importance  to  the 
chemist,  that  every  well  furnished  labratory  is  provided  with 
means    for   its    abundant  preparation.     A  copper  still,  well 
tinned,  and  connected  with  a  pure  block-tin  worm  or  conden- 
ser, answers  very  well  to  produce  the  common  supply.     But 
very  accurate  operations  require   it  to  be  again  distilled  in 
clean  vessels  of  hard  glass.     The  solvent  powers  of  pure 
water  are  in  some  cases  much  greater  than  of  common  water. 

408.  The  solvent  powers  of  water  far  exceed  those  of  any 
other  known  fluid.     Nearly  all  saline  bodies  are,  to  a  greater 
or  less  extent,  dissolved  by  water,  and  heat  generally  aids  this 
result.     In   the  case  of  common  salt,  however,  and  a  few 
other  bodies,  cold  water  dissolves  as  much  as  hot.     Gases  are 


What  is  the  weight  of  a  cubic  inch  of  water  ?     405.  What  is  the 
boiling  point  of  water  ?     What  departures  from  this  law  are  named  ? 

406.  What  does  common  water  contain  ?     Why  is  it  never  pure  ? 

407.  How  is  pure  water  obtained  ?     408.  How  are  the  solvent  powers 
of   water  ?     Give  examples. 

21* 


246  NON-METALLIC    ELEMENTS. 

nearly  all  absorbed  or  dissolved  in  cold  water,  and  some  of 
them  to  a  very  great  extent,  while  others,  as  hydrogen  and 
common  air,  are  very  little  taken  up.  They  are  all  expelled 
again  by  boiling.  -  Hot  water  dissolves  many  bodies  which 
are  quite  insoluble  in  cold,  especially  when  aided  by  small 
portions  of  alkaline  matter.  The  waters  of  the  hot  springs 
in  Iceland  and  in  Arkansas  deposit  much  silicious  matter 
before  held  in  solution ;  and  Dr.  Turner  found  that  common 
glass  was  dissolved  in  the  chamber  of  a  steam-boiler  at  300°, 
and  stalactites  of  silicia  were  formed  from  the  wire  basket  in 
which  the  glass  was  suspended.  This  is  a  subject  of  great 
importance  in  many  geological  speculations. 

409.  The  powers  of  water  as  a  chemical  agent  are  very 
various  and  important.     From  its  neutral,  mild,  and  salutary 
character,  we  are  accustomed  to  regard  it  only  as  a  negative 
substance,  possessed  of  little  energy,  while  it  is  in  fact  one  of 
the    most    important     chemical    agents    in   our     possession. 
Besides  its   solvent  powers,  we  know  that  it  combines  with 
many  substances,    forming  a  large  class  of  hydrates;  hy- 
drate of  lime  and  potash  are  examples.     It  is  also,  as  we 
have  seen,  (292,)  essential  to  the  acid   properties  of  common 
sulphuric,  phosphoric,  and  nitric   a/ids,  acting  here  the  part 
of  a    much    more   energetic  base  than  in  the  hydrates.     It 
forms  an  essential  part  in  the  composition  of  many  neutral 
salts,  and  can  be  replaced  in  composition  by  other  neutral 
saline  bodies;  while  as  water  of  crystallization  it  discharges 
still  another  important  and  distinct  function,  the  crystalline 
forms  of  many  salts   being  quite  dependent  on  its  presence 
in  atomic  proportions. 

410.  Peroxyd  or  Binoxyd  of  Jfydrogen. — This   curious 
compound  was  discovered   in  1818   by  M.    Thenard.     It  is 
difficult  of  preparation  by  any  process  ;  but  that  lately  recom- 
mended by  M.  Pelouze  is  the  best.     It  consists  in  decompos- 
ing the  peroxyd   of  barium  by  exactly  as  much  very  cold 
solution   of  hydrofluoric  acid,  (fluosilicic  or  phosphoric  acid 
may  be  used  as  well,)  as  will   saturate  the  base,  the  whole 
being  precipitated  as  fluorid   of  barium.     The  reaction  may 
be  expressed  thus : 

How  does  hot  water  act  in  this  respect  ?  Mention  facts.  409. 
What  are  the  powers  of  water  as  a  chemical  agent  ?  How  does  it 
act  in  sulphuric  acid,  &c.  ?  How  in  many  salts  ?  410.  What  is  the 
peroxyd  of  hydrogen  ?  By  whom,  and  when  discovered  ?  How  is  it 
prepared  ? 


COMPOUNDS    OP   HYDROGEN.  247 

Peroxyd  of  barium.  Hydrofluoric  acid.  Fiuorid  of  barium.  Peroxyd  of  Hydrogen 

BaO2       +       HF  BaF        +        HO2. 

The  pcroxyd  of  hydrogen  remains  dissolved  in  the  water, 
which  is  freed  from  the  insoluble  fluoric!  of  barium  by  filtra- 
tion, and  then  evaporated  in  the  vacuum  of  an  air-pump  by 
the  aid  of  the  absorbing  power  of  sulphuric  acid. 

411.  Properties. — The  properties  of  this   body  are  very 
remarkable.     When  as   free  from  water  as  possible,  it  is  a 
syrupy  liquid,  colorless,   almost  inodorous,  transparent,  and 
possessed  of  a  very  nauseous,  astringent,  and  disgusting  taste. 
Its  specific  gravity  is  1*453,  and   no  degree  of  cold  has  ever 
reduced  it  to  the  solid  form.     Heat  decomposes  it  with  effer- 
vescence and  the  escape  of  oxygen  gas.     It  can  be  preserved 
only  at  a  temperature  below  50°.     The  contact  of  carbon  and 
many  metallic  oxyds    decompose  it,  often  explosively,  and 
with   evolution   of  light.     No   change  is  suffered  by  many 
bodies  which  decompose  it ;  but  several  oxyds,  as  those  of 
iron,  tin,  manganese,  and  others,  pass  to  a  higher  state  of 
oxydation.     Oxyd     of    silver,    and     generally    those   oxyds 
which  lose  their  oxygen   at  a  high  temperature,  are  reduced 
to  a  metallic  state  by  this  decomposition.     When  diluted,  and 
especially  when  acidulated,  the  peroxyd  of  hydrogen  is  more 
stable.     This  body  is  dissolved  by  water  in  all  proportions, 
bleaches  litmus  paper,  and  whitens  the  skin.     None  of  its 
compounds  are  known,  nor  docs  it  seem  to  have  any  tendency 
to  combine  with  other  bodies. 

412.  Ozone.  —  There   is   a  remarkable    body    given    off* 
during  the  electrolysis  of  water,  having  a  peculiar  odor,  and 
very  volatile.     The  same  odor  is  perceived  when  a  series  of 
electrical  sparks  is  passed  through  a  confined  portion  of  air ; 
and   lastly,  when   phosphorus  is  slowly  oxydized  in  a  large 
volume  of  air,  a  peculiar  odor  is  perceived,  which  is  identical 
with  the  foregoing,  and  does  not  belong  either  to  phosphorus 
or  any  of  its  compounds.     This  is  the  ozone  of  Professor 
Schonbein,  of  which  much   has  been  said   in  the  scientific 
journals.     It  bleaches   powerfully,  and   converts  many  pro- 
toxyds  (as  those  of  calcium  and   barium)  to  peroxyds,  and 
sulphurous   to  sulphuric  acid.     It  is  decomposed   by   heat, 
water,  and  oxygen,  like  peroxyd  of  hydrogen  ;  and  the  latest 


Explain  the  reaction.  4 11. 'What  are  its  properties  ?  412.  What 
remarkable  body  is  named  in  connection  with  binoxyd  of  hydrogen  ? 
How  is  it  produced  ?  What  are  its  properties  ?  What  is  its  real 
nature  ? 


248  NON-METALLIC    ELEMENTS. 

opinion  is,  that  ozone  is  an  allotropic  condition  (415)  of 
oxygen,  analogous  to  the  double  condition  of  chlorine,  and 
many  other  elements.  Oa  and  O/3  may  be  employed  to  ex- 
press these  two  states. 

4.  Compounds  of  Hydrogen  with  the  II.  and  III.  Classes. 

413.  The  eminently  electro-positive  character  of  hydro- 
gen causes  it  to  form  well  characterized  and  analogous  com- 
pounds with  all  the  members  of  the  oxygen  group.     These 
binary  compounds  have  frequently  been  called  the  hydracids, 
in   distinction    from    those   acid    bodies  already  considered, 
which,  in  parity  of  language,  have  been  called  the  oxacids. 

It  is  however  more  in  accordance  with  facts  and  the 
principles  of  a  philosophic  classification,  to  look  upon  these 
bodies  as  having  in  reality  the  same  essential  characters  as 
the  chlorids,  bromids,  iodids,  &c.,  of  other  highly  electro- 
positive bases.  We  have  already  remarked,  (199,  note,) 
that  the  principles  of  our  nomenclature  require  all  these 
bodies  to  be  called  after  their  electro-negative  elements,  i.  e. 
chlorohydric,  bromohydric,  &c. ;  but  common  usage  having 
established  the  other  names,  we  shall  not  on  the  present 
occasion  depart  from  them.  The  compounds  of  hydrogen 
to  be  considered  under  this  head  are — 

Composition  by  weight. 

Symbol.  Hydrogen.        Chlorine. 

Hydrochloric  acid,  HC1  1  35-41 

Bromine. 
Hydrobromic  acid,  HBr  1  78-26 

Iodine. 
Hydriodic  acid,  HI  1  126-36 

Fluorine. 
Hydrofluoric  acid,  HF  1  18-70 

Sulphur. 
Hydrosulphuric  acid,          HS  1  16-09 

Selenium. 
Hydroselenic  acid,  HSe  1  39-57 

Tellurium. 
Hydrotelluric  acid,  HTe  1  64-14 

414.  Action  of  Hydrogen  with  Chlorine. — These  bodies 
have  a  very   powerful   affinity  for  each  other,  and   combine 

413.  What  is  said  of  the  compounds  of  hydrogen  with  the  oxygen 
group  ?  How  are  the  hydracids  now  looked  upon  ?  Enumerate  these, 
and  give  their  formulas  and  constitution  on  the  board.  What  is  re- 
markable in  this  group  ?  414.  What  of  the  affinity  of  chlorine  and 
hydrogen  ? 


COMPOUNDS  OF  HYDROGEN.  249 

under  ordinary  circumstances,  when  mixed  in  the  gaseous 
state.  Their  affinity  is  such  as  to  enable  chlorine  to  decom- 
pose water  (264)  and  appropriate  its  hydrogen.  In  this  way 
chlorine  becomes  one  of  the  most  powerful  oxydizing  agents 
known,  since  the  nascent  oxygen  given  off  during  the 
decomposition  of  water  attacks  any  third  body  which  may 
be  present  that  is  capable  of  combining  with  it. 

415.  The  combination  of  hydrogen  with  chlorine  de- 
pends on  the  action  of  light.     We  have  already  remarked 
that  light,  (264,)  and  especially  the  violet  ray,  gives  chlorine 
the   power  to  decompose  water.     Chlorine  prepared  in  the 
dark,  and   mingled  with   hydrogen,  the  mixture  being  also 
kept  in  the  dark,  will  not  combine  with  hydrogen  nor  decom- 
pose water,  and  the  two  bodies  seem  altogether  indifferent 
to  each  other.     It  has  been  long  known  that  the  direct  rays 
of  the  sun  would  cause  the  explosive  union  of  this  mixture ; 
and  Dr.  Draper  has  shown  that  chlorine  gas  which  has  been 
exposed   alone  and  dry  to  the  sun's  light,  has  acquired  the 
power  of  forming  this  explosive  union  with   hydrogen,  even 
in  the  dark,  and  retains  it  for  some  time.     The  result  of  this 
union  is  hydrochloric  acid.     We  see  in  this  fact  the  best 
proof  of  the    double    state   which    chlorine    can    assume, 
(allotropism,)  and  which  it  possesses  in  common  with  several 
other  bodies.     In  its  passive  state,  (as  prepared  in  the  dark,) 
it  actually  replaces  hydrogen   in  the  constitution  of  many 
organic   bodies,  or,   in   other    words,   assumes   an   electro- 
positive condition.     The  effect  of  the  sun's  light  is  to  confer 
a  new  state  upon  it,  probably  by  a  new  arrangement  of  its 
molecules,    (218,)    by   which    its   character    is   completely 
changed.     It   then   becomes    highly   electro-negative.     We 
have  then  in  chlorine  an  instance  of  an  element  capable  of 
acting  in  opposite  characters  under  different  circumstances. 

416.  Hydrochloric   Acid,   Chlorid  of  Hydrogen,  Mu- 
riatic Acid. — This  compound  is  formed  from  the  action  of 
dilute   sulphuric  acid  on  common  salt,  or  chlorid  of  sodium. 
The  reaction  may  be  thus  described : 

NaCl  +  SO3,HO=:  (NaO,  SO)  -f  C1H. 
No  process  is  more  simple.     A  little  heat  is  required,  and 

How  is  it  shown?  How  does  chlorine  assist  in  oxydation  ?  415. 
On  what  does  the  combination  of  hydrogen  and  chlorine  depend  ? 
Explain  this  as  illustrated.  How  does  chlorine  appear  to  us  under 
this  view  ?  416.  How  is  hydrochloric  acid  formed  ?  What  other 
names  has  it  ? 


250 


NON-METALLIC    ELEMENTS. 


the  gas  being  entirely  absorbed  by  water,  must  be  collected 
over  mercury,  or  in  dry  vessels  by  displacement  of  air. 

417.  Properties. — Chlorid  of  hydrogen  is  a  gas  having  a 
density  of  1-269.     It  is  colorless,  has   the  greatest  avidity 
for  water,  forms  an  acid  fog  by  combining  with  the  moisture 
of  the  air,  which   attacks  the  skin,  has  a  most  suffocating 
effect  in  respiration,  and  greatly  irritates  the  eyes.     It  is  by 
no   means,    however,  so  unpleasant   as   chlorine.     With    a 
pressure  of  26-30  atmospheres,  at  32°,  it  becomes  a  colorless 
liquid,  which  no  degree  of  cold  yet  employed  has  solidified. 

418.  This  gas  dissolves  largely  in  cold  water,  forming 
an  acid  solution,  which  is  the  common  muriatic  acid  of  com- 
merce, or  spirit  of  salt  of  the  shops.     At  common  tempera- 
tures water  will  absorb   nearly  420   times  its  own   bulk  of 
muriatic  acid  gas.     The  solution  is  a  powerful  acid,  of  great 

use  in  the  arts  and  in  the 
chemical  laboratory.  It 
may  be  prepared  pure  by 
an  arrangement  of  appa- 
ratus like  the  figure. 
The  common  salt  is  con- 
tained in  a  large  flask 
(a)  which  is  fitted  with  a 
cork  having  two  tubes, 
one  of  which  (b)  bends 
over  and  dips  into  the 
middle  bottle,  (c,)  which 
contains  a  little  water  to 
wash  the  gas.  The  last 
bottle  (d)  is  filled  with 
pure  water,  kept  cool  by 
ice  or  a  freezing  mixture ; 
the  gas,  after  being  wash- 
ed in  the  middle  bottle, 
(c,)  passes  by  the  second 
bent  tube  (e)  to  the  last 
bottle,  where  it  is  absorb- 
ed. Sulphuric  acid,  equal  in  weight  to  the  salt  employed,  is 
turned  in  successive  portions  upon  the  salt  through  the  recurved 


417.  What  is  its  condition  ?  What  its  properties  ?  418.  How 
much  of  this  gas  does  water  absorb  ?  What  is  the  solution  called  ? 
Explain  the  apparatus  by  which  it  is  made. 


COMPOUNDS  OF  HYDROGEN.  251 

funnel  tube  (f)  shown  on  a  larger  scale  in  the  second  figure. 
This  is  called  a  safety  tube ;  it  is  bent  twice  on  itself,  and 
has  a  ball  blown  on  one  of  the  turns.  When  a  liquid 
is  poured  in  at  the  funnel-top,  it  must  rise  as  high  as  the 
turn,  before  it  can  pass  down  into  the  flask,  and  a  por- 
tion of  the  fluid  is  therefore  always  left  behind  in  the 
bend,  which  serves  as  a  valve  against  the  entrance  of 
air,  and  also  effectually  prevents  an  explosion  of  the 
flask  in  case  the  tube  of  delivery  should  become  stop- 
ped. It  acts  also  as  a  safety  tube  against  the  danger 
of  absorption,  and  the  rushing  back  of  the  fluid  in  the 
bottles  by  atmospheric  pressure,  in  case  the  gas  in  the 
flask,  should  cease  to  be  given  out.  This  accident, 
which  not  unfrequently  happens,  is  also  provided  for  by 
the  large  open  tube  (g)  in  the  middle  bottle  through 
which  the  bent  tube  descends  into  the  fluid,  which  is  at  the 
same  time  open  to  the  air.  This  arrangement  completely 
prevents  the  loss  of  the  product  in  the  last  bottle,  (dt) 
which,  in  case  of  a  stoppage  of  the  gas,  would  otherwise,  by 
the  partial  vacuum  resulting,  be  all  driven  back  into  the  first 
bottle,  and  finally  into  the  flask. 

The  joints  about  the  corks  are  made  tight  by  a  little 
yellow  wax  melted  over  them  by  a  warm  iron  rod.  Heat  is 
applied  by  means  of  the  furnace,  (o,)  or  by  a  lamp.  This 
same  apparatus  may  be  employed  in  making  solutions  of  all 
the  absorbable  gases,  and  is  so  simple  as  to  be  within  the 
means  of  the  humblest  laboratory ;  the  essential  parts  being 
only  wide-mouthed  bottles,  glass  tubes,  a  gas  bottle  or  flask, 
and  a  few  corks. 

419.  Pure  hydrochloric  acid  is  a  colorless,  highly  acid, 
fuming  liquid,  having  a  specific  gravity  of  1*8  when  satu- 
rated ;  it  then  contains  42  parts  in  a  hundred  of  real  acid. 
Its  purity  is  tested  by  its  leaving  no  residue  on  evaporating  a 
drop  or  two  on  clean  platinum,  and  by  its  giving  no  milkiness 
when  a  solution  of  chlorid  of  barium  is  added  to  it,  [sulphuric 
acid.]  Neutralized  by  ammonia,  it  ought  not  to  become 
black  when  hydrosulphuret  of  ammonium  is  added,  [iron.] 
It  may  always  be  obtained  pure,  by  diluting  the  acid  of  com- 
merce until  it  has  the  specific  gravity  of  1*11,  and  distilling. 
The  product  is  colorless  and  pure,  having  the  same  density. 


What  is  the  action  and  use  of  the  safety  tube  ?    419.  What  are 
the  characters  of  pure  hydrochloric  acid  ?     How  is  it  purified  ? 


252  NON-METALLIC    ELEMENTS. 

The  commercial  acid  is  always  impure,  and  colored  yellow 
by  free  chlorine,  iron,  and  organic  matters.  A  solution  of 
nitrate  of  silver  detects  the  presence  of  a  soluble  chlorid,  or 
of  hydrochloric  acid,  by  forming  with  it  a  white  curdy  pre- 
cipitate of  chlorid  of  silver,  which  is  soluble  in  ammonia,  but 
insoluble  in  acids  or  water.  This  acid  is  an  electrolyte, 
(236,  1,)  and  is  also  decomposed  by  ordinary  electricity.  A 
mixture  of  muriatic  acid  gas  with  oxygen,  passed  through  a 
red-hot  tube,  produces  water  and  chlorine. 

420.  Tiie  uses  of  hydrochloric  acid  are  very  numerous. 
Its  decomposition  by  oxyd  of  manganese  affords  the  easiest 
mode  of  procuring  chlorine.     It  dissolves  a  great  number 
of  metals  forming  chlorids,  from  which  these  metals  may  be 
obtained   in  their  lowest  state  of  oxydation.     In   chemical 
analysis  and  the  daily  operations  of  the  laboratory  it  is  of 
indispensable  use.     Mingled   with   half  its  own  volume  of 
strong  nitric  acid,  it  makes  the  deeply-colored,  fuming  and 
corrosive  aqua  regia.     This  mixed  acid   evolves  much  free 
chlorine,  which   in   its   nascent  state   has   power  to  dissolve 
gold,  platinum,  &c.,  forming  chlorids  of  those   metals,  and 
not  nitromuriates,  as  was   formerly  supposed.     As  soon  as 
all  the  chlorine  is  evolved,  this  peculiar  power  of  the  aqua 
regia  is  lost. 

421.  Hydrochloric  acid  is  made  in   the  arts  in  immense 
quantities,  especially   in   England,  where  the  carbonate  of 
soda  is  largely  made  from  common  salt,  (chlorid  of  sodium,) 
by  the  action  of  sulphuric  acid.     The  vast  volumes  of  chlorid 
of  hydrogen  which  are  evolved   in   this  process,  are  by  law 
required   to   be  condensed,  to  avoid  the  injury  to  vegetation 
and  health  formerly  experienced,  from  their  being  allowed  to 
escape    into   the   atmosphere.      In    this    way,    hydrochloric 
acid  is  made  as  an  incident  to  other  processes,  in  such  quan- 
tifies as  to  overstock  tho  market. 

422.  Hydrobramic  Acid — Bromid  of  Hydrogen. — Hy- 
drogen and    bromine  do    not  act    upon    each    other  in    the 
gaseous  state,  even   by  the  aid  of  the  sun's  light ;  but  a  red 
heat  or  the  electric  spark  causes   union, — only  among  those 
particles,  however,  which  are  in   immediate  contact  with  the 
heat,  the  action  not  being  general.     Hydrobromic  acid  may 


What  impurities  have  the  commercial  acids  ?  How  are  they  de- 
tected ?  420.  What  are  its  uses  ?  What  is  aqua  regia  ?  What  use 
has  it,  and  on  what  dependent  ?  421.  What  is  said  of  the  abundance 
of  this  acid?  422.  Kow  do  hydrogen  and  bromine  a«t  .together  ? 


COMPOUNDS  OF  HYDROGEN.  253 

be  prepared  by  the  reaction  of  moist  phosphorus  on  bromine 
in  a  glass  tube.  The  gas  given  off  must  be  collected  over 
mercury.  It  is  composed,  like  hydrochloric  acid,  of  equal 
volumes  of  its  elements  not  condensed.  Its  specific  gravity 
is  2*731,  and  it  is  condensed  by  cold  and  pressure  into  a 
liquid.  In  its  sensible  properties  it  bears  a  close  resemblance 
to  hydrochloric  acid.  With  the  nitrates  of  silver,  lead,  and 
mercury,  it  gives  white  precipitates  similar  to  the  chlorids. 
It  has  a  strong  avidity  for  water,  and  dissolves  largely  in  it, 
giving  out  much  heat  during  the  absorption.  The  saturated 
aqueous  solution  has  the  same  reactions  as  the  dry  acid,  and 
fumes  with  a  white  cloud  in  contact  with  air.  It  dissolves  a 
large  quantity  of  free  bromine,  acquiring  thereby  a  red  tint. 

423.  Hydriodic  Acid—Iodid  of  Hydrogen. — This  body 
may  be  formed  by  the  direct  union  of  its  elements  at  a  red 
heat,  but  is  more  easily  prepared  by  acting  on  iodine  and 
water  with  phosphorus,  by  which  means  the  gas  is  given  out 
in  large  quantities.  The  action  of  phosphorus  and  iodine  is 
violent  and  dangerous,  but  may  be  regulated  and  made  safe 
by  putting  a  little  powdered  glass  between  each  layer  of 
phosphorus  and  iodine.  Phosphoric  acid  is  formed  and 
remains  in  solution,  while  the 
hydriodic  acid  gas  is  given  out,  and 
may  be  collected  over  mercury,  or 
dissolved  in  water.  The  dry  gas 
has  a  great  avidity  for  water.  Its 
specific  gravity  is  4-385,  air  =  1  ; 
being  formed  like  the  two  last  of 
one  volume  of  each  element  uncon- 
densed.  Cold  and  pressure  reduce 
it  to  a  clear  liquid,  which,  at  — 60°  Fahr.,  freezes  into  a 
colorless  solid,  having  fissures  running  through  it  like  ice. 
It  forms  a  very  acid  fluid  by  solution  in  water,  which  has, 
when  saturated,  a  specific  gravity  of  1-7,  and  emits  white 
fumes. 

The  aqueous  solution  is  also  prepared  by  transmitting  a 
current  of  hydrosulphuric  acid  through  water  in  which  free 
iodine  is  suspended.  The  gas  is  decomposed,  sulphur  set 


How  is  hydrobromic  acid  prepared  ?  What  character  has  it  ?  423. 
How  is  hydriodic  acid  prepared  ?  What  is  the  reaction  ?  What  are 
the  properties  of  the  gas  ?  How  else  may  the  aqueous  solution  be 
prepared  ? 

22 


254  NON-METALLIC    ELEMENTS. 

free,  and  hydriodic  acid  produced,  which  is  purified  from 
free  hydrosulphuric  acid  by  boiling,  and  from  sulphur  by 
filtration. 

424.  The  aqueous  hydriodic  acid  is  easily  decomposed 
by  exposure   to   the  air,  iodine   being  set   free.     It    forms 
characteristic,  highly  colored   precipitates  with  most  of  the 
metals,  particularly  with  lead,  silver,   and   mercury.     Bro- 
mine decomposes  it,  and  chlorine  decomposes  both  hydro- 
bromic   and    hydriodic    acids,    thus    showing    the    relative 
affinities   of  these    bodies    for   hydrogen.     This   acid   is   a 
valuable  reagent ;  its  presence  in  solution  is  easily  detected 
by  a  cold  solution  of  starch  with  a  few  drops  of  strong  nitric 
or  sulphuric  acid,  which    instantly  gives   the   fine    charac- 
teristic blue  of  the  iodid  of  starch. 

425.  Hydrofluoric  Acid,  or  Fluorid   of  Hydrogen,  is 
obtained  from  the  decomposition  of  fluor-spar  by  strong  sul- 
phuric acid.     The  operation  must  be  performed  in  a  retort 
of  pure  lead,  silver,  or  platinum,  and  requires  a  gentle  heat. 
The  fluorine  leaves   the  lime  and  joins  the  hydrogen  of  an 
atom  of  water  in  the  acid,  forming  hydrofluoric  acid,  while 
sulphate  of  lime  remains  behind  ;  or,  expressed  in  symbols, 

Fluorid  of  Sul.  acid.  Sul.  lime.  Fluorid  of 

calcium.  hydrogen. 

CaF        +        S03,  HO  S03,  CaO        +        HF 

The  fluor-spar  must  be  pure,  and  especially  free  from  silica. 

426.  Propertied. — Hydrofluoric  acid    is  a  gas  which  at 
32°   is  condensed   into  a  colorless   fluid,  with  a  density  of 
1*069,  which  can   be  preserved   as  a  fluid  even  at  higher 
temperatures  in  well   stopped   bottles  of  silver  or  lead.     Its 
avidity  for  water  is  extreme,  and  when  brought  in  contact 
with   it,   the   acid   hisses   like   red-hot   iron.      Its   aqueous 
solution,  as  well  as  the  vapor  of  the  acid,  attacks  glass  very 
powerfully,  and  is  often  used   to  etch  it,  as,  for  example,  in 
marking   the   test   bottles    in    the    laboratory,   or    biting   in 
designs  traced  in  wax  on  the  surface  of  glass  plates.     It  is  a 
powerful   acid,  with  a  very  sour  taste,  neutralizes   alkalies, 


42-1.  What  properties  has  the  aqueous  hydriodic  acid  ?  What  are 
the  mutual  relations  of  iodine,  bromine,  and  chlorine,  as  shown  by 
their  compounds  with  hydrogen  ?  How  is  the  presence  of  hydriodic 
acid  detected  ?  425.  What  is  hydrofluoric  acid'?  Explain  the  reac- 
tion by  which  it  is  produced.  426.  What  are  the  properties  of  this 
body  ?  What  is  its  most  remarkable  affinity  ? 


COMPOUNDS  OF  HYDROGEN.  255 

and  permanently  reddens  blue  litmus.  On  some  of  the 
metals  its  action  is  very  powerful ;  it  unites  explosively  with 
potassium,  evolving  heat  and  light.  It  attacks  and  dissolves, 
with  the  evolution  of  hydrogen,  certain  bodies  which  no  other 
acid  can  affect,  such  as  silicon,  zirconium,  and  columbium. 

Silicic,  titanic,  columbic,  and  molybdic  acids  are  also 
dissolved  by  it. 

427.  Hydrofluoric  acid  is  a  most  dangerous  body  to 
experiment  with.     It  attacks  all  forms  of  animal  matter  with 
wonderful  energy.     The  smallest  drop  of  the  concentrated 
acid    produces   ulceration  and   death,  when  applied  to  the 
tongue  of  a  dog.     Its  vapor  floating  in  the  air  is  very  corro- 
sive, and   should   be  carefully  avoided.     If  it  falls,  even  in 
small  spray,  on  the  skin  of  the  hand  or  any  part  of  the  body, 
it  produces  a  malignant  ulcer,  which  it  is  very  difficult  to  cure. 
Any  considerable  quantity  of  it  would  prove  fatal.     For  this 
reason  it  is  quite  inexpedient  for  unexperienced  persons   to 
attempt  its   preparation.     By  using  a  weaker  sulphuric  acid, 
however,  and   having  water  in   the   condenser,  no    risk   is 
incurred.     As  before  remarked,  it  attacks  silica  more  pow- 
erfully than  any  other  body,  and  their  mutual  affinity  is  one 
of  the   most   powerful  known  to  us.     This  fact  puts  us  in 
possession  of  an  admirable  mode  of  analyzing  silicious  min- 
erals, when  we  do  not  wish  to  fuse  them  with  an  alkali.     By 
exposing  the   fine  powder  of  the  moistened  mineral  to  the 
vapor  of  the  hydrofluoric  acid,  all  the  silica  is  taken  up  and 
carried  away  as  hydrofluosilicic  acid  gas,  (364.) 

428.  The   hydrofluoric   acid  was   formerly  called  fluoric 
acid,  and  the  fluor  spar,  a  fluate  of  lime.     We  now  know 
that  this  mineral  is  a  Jluorid  of  calcium,  in  exact  analogy 
with  the  chlorid  of  sodium,  and  a  very  numerous  class  of 
similar  binary  compounds,  with  which  our  study  of  the  metals 
will  familiarize  us. 

429.  Hydrosulphuric  Acid — Sulphureted  Hydrogen. — 
When  the  protosulphuret  of  iron  or  the  sulphuret  of  antimony 
is  treated  with  a  dilute  acid,  effervescence  occurs,  and  a  gas 
is  given  out  having  a  most  disgusting  fetid   odor,  which  at 
once  reminds  us  of  the  nauseous  smell  of  bad  eggs.     This 

What  are  its  relations  to  the  metals  ?  What  acids  are  dissolved 
by  it  ?  427.  How  does  it  affect  animal  matter  ?  What  caution  is 
given  ?  What  analytical  use  is  named  for  this  acid  ?  428.  What 
was  this  acid  formerly  called  ?  What  more  exact  knowledge  do  we 
now  possess  ?  429.  What  is  hydrosulphuric  acid,  and  how  set  free  ? 


256  NON-METALLIC   ELEMENTS. 

is  sulphuretcd  hydrogen  gasj  one  of  the  most  useful  reagents 
to  the  chemist,  especially  in  relation  to  the  metallic  bodies. 

430.  Properties. — This  gas  is  colorless,  and  less  offensive 
in   quantity  than  when  the  air  is  contaminated  with  only  a 
trace.     It  burns  with  a  pale  blue  flame  like  that  of  sulphur, 
water  and  sulphurous  acids  being  the  products.     If  oxygen  is 
mingled  with  it,  and   the   mixture  ignited,  or  touched  with  a 
match,  it  explodes  with   a  shrill  sound,  sulphur  is  deposited, 
and  water  formed.     When  the  oxygen  is  in  the  proportion  of 
150  measures  to  100  of  sulphurcted  hydrogen,  the  combus- 
tion   is  complete,  and  only  sulphurous  acid  and  water  are 
formed.     Strong  nitric  acid  and  chlorine  gas  also  decompose 
it,  and  sulphur  is  set  free.     It  has  a  specific  gravity  of  1-171, 
and   100  cubic  inches  of  it  weigh  36-33  grains.     At  a  tem- 
perature  of  50°,  it   is  made  liquid  by  a  pressure  of  14-5 
atmospheres,  and  at   —122°  Kahr.,  it  freezes  into  a  white 
confused    crystalline   solid,   not    transparent,    and  which    is 
much  heavier  than  the  fluid,  sinking  in  it  readily. 

431.  Cold  water  dissolves  its  own  volume  of  sulphurcted 
hydrogen,  and    acquires    its    peculiar   odor  and    properties. 
When  recently  prepared,  it   takes  the  place  of  the  gas  ns  a 
test ;  but  it  is  so  easily  decomposed    by  contact  with  the  air, 
with  the  deposition  of  sulphur,  that  it  cannot  long  be  kept  on 
hand. 

The  student  should  always  have  at  hand  in  the  laboratory 
a  little  gas  bottle,  like  the  figure,  holding 
some  fragments  of  protosulphuret  of  iron, 
to  which,  when  the  gas  is  wanted,  a  little 
water  is  added  and  then  a  few  drops  of 
oil  of  vitriol.  Effervescence  ensues,  and 
the  gas  is  delivered  by  the  bent  tube, 
into  any  solution  which  we  desire  to  treat 
with  it. 

432.  Properties  and  Uses. — This   gas    posesses  the  pro- 
perties of  an  acid;  its  aqueous  solution  reddens  litmus  paper, 
and  it  forms  compounds  with  many  bases.     It  precipitates 

What  other  name  has  it  ?  430.  What  are  its  properties  ?  How 
does  it  smell  ?  Is  it  combustible  ?  How  does  it  burn  when  mingled 
with  oxygen  ?  Is  it  condensable  to  a  fluid  ?  431.  How  much  of  it 
will  water  dissolve  ?  What  properties  has  the  solution  ?  What  ob- 
jection to  its  use  ?  What  mode  is  preferred  for  using  this  reagent  ? 
432.  How  is  it  seen  to  be  an  acid  ?  What  are  its  properties  and 
uses? 


COMPOUNDS  OF  HYDROGEN. 


257 


from  solution  all  the  metals  whose  sulphurets  are  insoluble  in 
water,  often  giving  the  most  characteristic  precipitates.  It 
thus  enables  the  chemist  to  effect  many  separations  of  metals 
with  ease  and  certainty,  and,  as  before  remarked,  is  one  of 
his  most  valuable  reagents.  Its  presence  in  solution  is  at 
once  detected  by  its  blackening  the  salts  of  lead.  Characters 
drawn  on  paper  with  a  solution  of  the  acetate  of  lead,  are  quite 
colorless  ;  but  a  stream  of  sulphureted  hydrogen  at  once 
causes  them  to  stand  forth  in  deep  black,  its  action  producing 
the  dark  sulphuret  of  lead. 

433.  It  occurs  in  solution  in  many  mineral  springs,  giving 
the  water  highly  valuable  medicinal  characters.     Such  springs 
are  much  resorted  to  in  this  country,  as  at  Avon,  N.  Y.,  and 
the  sulphur  springs  of  Virginia.     The  disgust  at  first  felt  at 
drinking  these  nauseous  waters  is  soon  overcome,  and  those 
patients  who   take   them    in    large    quantity   soon   observe 
the  gas  to  penetrate  their  whole  system  and  exude  in  their 
perspiration.     Silver  coin,    and   other   silver  articles  in  the 
pockets  of  such  persons  are  soon  completely  blackened  by  the 
coating  of  sulphuret  of  silver  formed  on  their  surface. 

434.  Although  salutary  when  used  in  the  stomach,  it  has 
been  found  to  be  a  deadly  poison  to  the  more  delicate  animals, 
even  when  present  in  the  air  in  only  a  small  quantity.     The 
operative  chemist  is,  however,  in  the  habit  of  breathing  it 
with  impunity,  for  the  atmosphere  of  an  active  laboratory  is 
often  impregnated  with  iL 

435.  When  sulphurous 
acid  and  sulphureted  hy- 
drogen gas   are   brought 
together  in  a  common  re- 
ceiving vessel,  mutual  de- 
composition   ensues,  and 
the  sulphur    of   both    is 
thrown  down  in  a  yellow 
cloud,  which  attaches  it- 
self to   the  sides   of  the 
vessel.      The 


same    ar- 


How  does  it  act  with  the  metals  ?  How  is  its  presence  detected  ? 
433.  How  does  this  gas  occur  in  nature  ?  What  use  is  made  of  sul- 
phureted waters  ?  434.  What  is  said  of  the  effect  of  this  gas  on  the 
system  of  animals  ?  435.  What  is  the  reaction  when  sulphuric  acid 
and  hydrosulphuric  acid  gases  are  mingled  ? 
22  * 


258  NON-METALLIC    ELEMENTS. 

rangement  of  apparatus  which  was  employed  for  illustrating 
the  formation  of  sulphuric  acid,  will  answer  in  this  experi- 
ment, substituting  the  materials  for  sulphurated  hydrogen  in 
the  flask,  (b.) 

436.  Hydroselenic    Acid  —  Seleniurcted    Hydrogen. — 
This  body  is  quite  similar  to  the  foregoing,  and  is  formed  in 
the  same  manner  by  decomposing  the  protosclcniuret  of  any 
of  the  more  easily  oxydized  metals,  with  a  weak  acid.     Its 
properties    and    reactions  are  very  similar  to    those   of  the 
hydrosulphuric  acid.     It  is  absorbed  by  water,  turns  the  skin 
brown,  and  irritates  the  mucous  membrane. 

Tellureted  Hydrogen  is  evolved  when  an  alloy  of  tin 
and  tellurium  is  acted  on  by  muriatic  acid:  it  reddens  lit- 
mus paper,  dissolves  in  water,  and  possesses  the  general 
habitudes  of  sulphureted  hydrogen. 

5.  Compounds  of  Hydrogen  with  Class  III. 

437.  The  compounds  which  hydrogen  forms  with  the  nitro- 
gen group,  are  strongly  contrasted  in  chemical  and  physical 
characters  with    the    remarkable  natural  family  which  has 
just  engaged  our  attention.     The  latter  are  all  acid,  and  gen- 
erally in  an  eminent  degree.     The  compounds  of  hydrogen 
with  the  nitrogen  group  are,  on  the  contrary,  either  neutral 
or  strongly  basic,  forming  a  series  of  salts  or  peculiar  com- 
pounds with  the   hydracids  before  named ;  thus  furnishing  a 
strong  reason  for  the  propriety  of  the  arrangement  which  we 
have  adopted  in  our  classification. 

The  compounds  named  under  this  head,  are — 

Composition  by  weight. 

Symbol.         Nitrogen.        Hydrogen. 
Ammonia,  NH3  14-06  3 

Phosphorus. 
Phosphureted  hydrogen,  PH3  31-38  3 

438.  Ammonia,  and  the  other  compounds  of  nitrogen  and 
hydrogen,  might  with    propriety  be   treated    under   organic 
chemistry,    since    hydrogen    and   nitrogen    do  not,   by  any 

436.  What  is  hydroselenic  acid,  and  how  allied  to  the  last  body  ? 
437.  What  is  said  of  the  compounds  of  the  hydrogen  with  the  nitro- 
gen group  ?  What  compounds  are  named  ?  Give  their  symbols  and 
composition.  438.  Where  might  ammonia  be  more  properly 
treated  of  ? 


COMPOUNDS  OP  HYDROGEN.  259 

direct  means,  unite  as  gases,  and  all  the  compounds  of  am- 
monia may  ultimately  be  traced  back  to  an  organic  origin. 
Ammonia  is  almost  invariably  one  of  the  products  of  the 
decomposition  of  those  organic  matters  which  contain  nitro- 
gen ;  and  we  shall  see,  when  we  come  to  study  these  bodies, 
that  their  elements  are  so  arranged,  that  we  might  expect  such 
a  result.  Ammonia  is  however  so  important  a  body  in  relation 
to  the  metals,  and,  in  fact,  as  a  reagent  in  nearly  all  chemical 
experiments,  that  we  shall  find  it  more  convenient  to  become 
acquainted  with  it  here,  than  at  a  later  period  of  our  studies. 

439.  History. — Sal  ammoniac   and  the  watery  solution 
of  ammonia  have  been  long  known,  and  probably  were  in 
use  among  the  ancients.     The  very  name  of  ammonia  indi- 
cates its  antiquity.*     The  sal-ammoniac,  sulphate  of  ammo- 
nia, and  ammonia-alum  are  found   among  the  products  of 
volcanoes.     Free  ammonia  is  exhaled  from  the  foliage  and 
found  in  the  juices  of  certain  plants,  in  the  perspiration  of 
animals,  in  iron  rust  and  absorbent  earths.     Rain  water  also 
contains  a  small  quantity  of  ammoniacal  salts,  washed  out  of 
the  atmosphere  ;  and  the  guano  so  much  valued  as  a  manure, 
is  rich  in  various  ammoniacal  compounds. 

440.  Preparation. — Ammonia  is    best  prepared    for  use 
by  decomposing  one  of  its  saline  compounds,  as  the  sal-am- 
moniac, by  an  alkali  and  heat.     For  this  purpose  equal  parts 
of  dry  powdered  sal-ammoniac  and  freshly  slaked  dry  lime 
are  well  mingled  and  heated  in  a  glass,  or  if  the  quantity  is 
considerable,  in  an  iron  vessel.     The  lime  takes  the  hydro- 
chloric acid,  forming  a  chlorid  of  calcium,  and  ammonia  is 
given  out  as  a  gas. 

441.  Properties. — The  dry  gas  is  colorless,  having  the 
very  pungent  smell  so  well  known  as  that  of  '  hartshorn.'' 
It  is,  when  undiluted,  quite  irrespirable,  and  attacks  the  eyes, 
mouth,  and  nose  powerfully.     It  is  alkaline,  and  has  fre- 
quently been  called  the  volatile  alkali.     Being  very  rapidly 
absorbed  by  water,  it  must  be  collected  over  mercury  or  in 

439.  What  is  known  of  the  antiquity  of  ammonia?  What  ammo- 
niacal compounds  are  found  native  ?  What  other  natural  sources  of 
ammonia  are  named  ?  440.  How  is  ammonia  prepared  ?  441. 
What  are  the  properties  of  this  gas  ? 


*  From  Amman,  an  epithet  by  which  Jove  was  known,  and  ammos, 
sand,  in  allusion  to  the  Egyptian  desert  of  Ammon,  where  sal-ammo- 
niac was  first  obtained. 


260 


NON-METALLIC    ELEMENTS. 


inverted  dry  vessels.  It  does  not  support  the  combustion  of 
a  candle,  and  does  not  burn  itself,  although  a  small  jet  of  the 
gas  will  burn  in  pure  oxygen,  and  the  flame  of  the  candle,  as 
it  goes  out,  is  slightly  enlarged  with  a  yellowish  fringe. 
Mixed  with  an  equal  volume  of  oxygen,  it  explodes  with  the 
electric  spark,  yielding  water  and  free  nitrogen.  The  dry 
gas  passed  through  a  red-hot  tube  is  completely  decomposed  ; 
iiOO  measures  of  the  gas  yielding  400  measures  after  decom- 
position, which  by  analysis  is  found  to  consist  of  300  measures 
of  hydrogen  and  100  of  nitrogen.  The  specific  gravity  of 
dry  ammonia  is  therefore  (192)  0-5893,  and  100  cubic 
inches  weigh  15-23  grains.  By  pressure  it  is  easily  con- 
verted into  a  liquid,  which  freezes  at  — 103°  Fahrenheit, 
producing  a  white  translucent  crystalline  solid,  which  is 
heavier  than  the  liquid. 

442.  The  solution  of  this  gas  in  water  (called  aqua  am- 
monitp,  and  sometimes  improperly  liquid  ammonia)  is  easily 
prepared,  and  possesses  all  the  peculiar  properties  of  the  gas. 
This  is  best  made  by  an  arrangement  like  the  annexed  figure, 
called  Woulfe's  apparatus.  This  consists  essentially  of  the 
gas  bottle  (a,)  which  contains  the  materials  to  generate  the 
gas,  and  is  placed  over  a  furnace.  Three  three-necked  bot- 
tles (b  c  d)  are  all  connected  with  a  by  a  scries  of  bent  tubes, 
(t  t  i  i).  The  gas  in  passing  from  a  by  t,  must  go  through 
a  portion  of  water  in  6,  where  it  is  absorbed.  It  is  prevented 
from  escaping  by  a  tube  in  the  middle  orifice,  (o,)  which  has 


its   lower  end  dipping  3  little  way  into  the  water  of  each 
bottle.     The  effect  of  this  is  to  cause  a  column  of  liquid  to 


How  does  it  affect  combustion  ?  How  is  it  analyzed  ?  What  is 
its  constitution  by  weight  and  volume  ?  What  is  its  density  ?  How 
does  cold  affect  it  ?  -142.  How  is  aqua  ammoniac  prepared  ?  Ex- 
plain Woulfe's  apparatus  anJ  its  mode  of  action. 


COMPOUNDS  OF  HYDROGEN.  261 

play  up  and  down  in  o,  as  the  pressure  of  the  gas  varies. 
Each  tube,  (i)  has  a  shorter  end  not  reaching  the  fluid. 
Things  being  thus  arranged,  and  the  tightness  of  all  the  joints 
and  corks  being  secured  by  bees-wax,  the  gas  bubbles  through 
o,  until  the  water  can  absorb  no  more ;  it  then  passes  on  to 
c,  and  then  to  df,  saturating  each  in  turn.  In  the  last  vessel 
is  a  little  mercury  under  which  the  bent  tube  (i)  dips,  with 
the  design  of  cfeating  a  slight  pressure  on  the  whole  appa- 
ratus, as  is  indicated  by  the  height  of  the  column  of  water  in 
ooo.  It  only  remains  to  keep  the  whole  (b  c  d)  cold,  and 
the  water  in  the  bottles  will  then  soon  become  saturated  with 
the  gas.  The  first  bottle,  is  usually  contaminated  by  foreign 
matters,  and  is  rejected.  Under  sulphuret  of  ammonium 
will  be  found  a  more  simple  form  of  the  same  apparatus 
formed  of  common  wide-mouthed  bottles. 

443.  The  saturated  aqueous  solution  of  ammonia  has  a 
specific  gravity  of  about  U'875,  is  colorless  and  transparent, 
and  exhales  the  gas  abundantly ;  when  it  is  of  this  density  it 
contains  32  per  cent,  of  real   ammonia.     It  must  be  kept  in 
tight  bottles,  to  prevent  the  loss  of  strength  and  the  absorp- 
tion of  carbonic  acid  gas  from  the  air.     It  has  all  the  charac- 
ters of  an  alkali,  it  saturates  the  most  powerful  acids,  and 
forms  a  series  of  salts  which  are  all  soluble  in  water,  and  are 
volatilized  at  a  red  heat.     It  boils  vehemently  at  130°,  and 
freezes  at  about  40°  below  zero.     It  browns  yellow  turmeric 
paper  temporarily,  but  the  original  color  returns  as  the  gas 
evaporates. 

444.  The  presence  of  ammonia  is  always  recognised  by 
its  odor,  by  its  action  on  turmeric  or  blue  cabbage  paper, 
(which  last  it  turns  green,)  and  especially  by  the  white  cloud 
of  muriate  of  ammonia  which  is  formed  on  bringing  a  rod 
moistened  with  hydrochloric  acid  near  it. 

445.  Hydrogen  and  Phosphorus  —  Phosphureted    Hy- 
drogen.— This  gaseous  body  is  formed  when  the  phosphuret 
of  calcium,  or  of  some  other  alkaline  metal,  is  acted  upon  by 
water ;    but  is  more  conveniently  prepared   by  employing 
quick-lime  recently  slaked,  water,  and  a  few  sticks  of  phos- 
phorus, in  a  small  retort,  the  ball  of  which  is  nearly  filled 
with  the  mixture.     A  gentle  heat  generates  the  gas,  which 

vVhat  properties  ?  443.  What  gravity  has  the  saturated  aqueous 
solution?  What  characterizes  its  salts?  444.  How  is  ammonia 
recognised  ?  445.  What  is  phosphorated  hydrogen,  and  how  prepared  7 


262 


NON-METALLIC    ELEMENTS. 


breaks  from  the  surface  of  the  water  (beneath  which  the 
beak  of  the  retort  dips  very  slightly)  in  bubbles,  that  inflame 


spontaneously  as  they  reach  the  air,  rising  in  beautiful 
wreaths  of  smoke,  which  float  in  concentric,  expanding  rings 
This  gas  loses  its  spontaneous  inflammability  by  standing  a 
time  over  water,  a  body  not  yet  obtained  in  a  separate  form 
being  deposited.  A  few  drops  of  ether  or  oil  of  turpentine 
destroy  this  property,  but  a  very  little  nitrous  acid  restores  it. 

446.  Properties.  —  This   gas    has   a   disgusting,    heavy 
odor,  like  putrid   fish,  which  is  far  more  annoying  than  sul- 
phureted   hydrogen.     It  is  transparent  and  colorless,  has  a 
bitter  taste,  and  if  dry  may  be  kept  unchanged  either  in  the 
light  or  dark.     It  is  deadly  when  breathed.     When  procured 
as  just  described,  it  acts  very  violently  with   oxygen   gas. 
If  bubbles  of  it  are  allowed  to  enter  a  jar  of  oxygen,  each 
bubble  burns  with   a  most  brilliant  light  and  a  sharp  ex- 
plosion.    The  mixture  of  even  a  very  small  quantity  with 
oxygen  would  be  quite  hazardous. 

447.  Phosphureted   Hydrogen   is   neither   alkaline   nor 
acid,  but  it  has  more  resemblance  to  an  alkali  than  to  an  acid, 
since  it  forms,  with  several   metallic  chlorids,  compounds 
analogous  to  those  which  ammonia  yields  with  the  same 
bodies.     It  also  combines  with  hydrobromic  and  hydriodic 
acids,  forming  colorless  crystalline  salts,  which  are  decom- 
posed by  water. 

448.  Three  Phosphurets  of  Hydrogen  have  been  distin- 
guished, which  have  the  formulas  PH,  PH2,  and  PH3.     The 


What  remarkable  property  has  the  fresh  gas  ?  Is  this  property 
constant  ?  446.  What  are  its  characters  ?  How  does  it  react  with 
oxygen  ?  447.  Is  this  gas  alkaline  or  acid  ?  What  compounds 
analogous  to  salts  does  it  form  ?  448.  How  many  and  what  phos- 
phurets  of  hydrogen  are  known  ? 


COMPOUNDS  OF  HYDROGEN.  263 

last  is  the  pure  gas,  the  second  is  the  spontaneously  in- 
flammable body,  and  the  first  is  a  solid. 

6.  Compounds  of  Hydrogen  with  the  Carbon  Group. 

449.  Carbon  and  hydrogen  unite  to  form  a  vast  number 
of  compounds,  all  of  which,  directly  or  indirectly,  are  the 
product  of  organic  life,  and  will  therefore  (with  two  excep- 
tions) be  discussed  more  properly  in  the  organic  chemistry. 

450.  The   carlo-hydrogens,   as   these   bodies   are   often 
called,  are  sometimes  solids  at  common   temperatures,  as 
paraffine  and  nephthaline ;  or  liquids,  as  the  oils  of  turpen- 
tine, lemons,  and  naphtha.     Two  of  them  are  gases,  and 
being  also  products  of  the  mineral  kingdom,  they  may  be 
properly  discussed   under  inorganic  chemistry.     We   refer 
to  the 

Composition  by  weight. 


Symbol.  Carbon.  Hydrogen. 

Light  carbureted  hydrogen  gas,         CHg  6              2 
Olefiant,  or   heavy  carbureted 

hydrogen  gas,                          CaHg  12              2 


451..  Light  Carbureted  Hydrogen  Gas;  Marsh  Gas; 
Fire  Damp  ;  or  Di-carburet  of  Hydrogen,  —  This  gas  occurs 
abundantly  in  nature,  being  formed  nearly  pure  by  the 
decomposition  of  vegetable  matter  under  water.  The  bubbles 
which  rise,  when  the  leaves  and  mud  of  a  stagnant  pool  or 
lake  are  stirred,  are  light  carbureted  hydrogen,  with  about 
•£$  of  carbonic  acid.  It  is  also  evolved  in  large  quantity  in 
coal  mines,  but  is  then  accompanied  by  several  other  gases. 
In  the  salt  regions  of  this  country  it  is  given  out  abundantly 
with  olefiant  gas  from  some  of  the  artesian  wells  bored  for 
salt  water.  It  is  also  sometimes  blown  out  in  a  strong  blast 
from  fissures  in  the  earth  ;  and  it  forms  a  part  of  the  gas 
employed  to  light  cities, 

452.  Preparation.  —  This  gas  may  be  prepared  artificially 
by  mixing  equal  parts  of  acetate  of  soda,  and  solid  hydrate 


449.  What  is  said  of  the  number  and  nature  of  the  compounds  of 
carbon  and  hydrogen  ?  Of  what  are  they  the  product  ?  450.  How 
do  the  carbo-hydrogens  present  themselves  ?  What  two  are 
referred  to?  Give  their  formulas  and  composition.  451.  What 
other  names  has  the  light  carbureted  hydrogen  ?  What  natural 
supplies  have  we  of  it  ?  452.  How  is  it  prepared  ? 


264?  NON-METALLIC    ELEMENTS. 

of  potash,  with  one  and  a  half  parts  of  quicklime.  The  mix- 
ture is  strongly  heated  in  a  retort,  when  the  gas,  perfectly 
pure,  is  disengaged  abundantly,  and  may  be  collected  over 
water.  The  hydrate  of  potash  decomposes  the  acetic  acid  at 
a  high  heat,  and  takes  from  it  two  equivalents  of  carbonic 
acid,  while  two  equivalents  of  marsh  gas  are  given  off; 
thus: 

Acetic  acid,    C4  H3  03  (  _  j  Carbonic  acid,     2  eq  C2      O4 
Water,  H  O    f  —  )  Marsh  gas,  2  eq  C2  H4 

C4  H4  04  C4  H4  O 

The  use  of  the  lime  is  to  keep  the  potash  from  acting  on  the 
glass  retort. 

453.  Properties. — This  gas  has  a  density  of  -5595,  and 
100  cubic  inches  of  it  weigh  17.41  grains.     It  is  composed 
of  one  volume  of  carbon  and  two  volumes  of  hydrogen,  or 
six  parts  by  weight  of  the  former  to  two  of  the  latter.     It  is 
neutral,  inodorous,  tasteless,  and  respirable  without  poison- 
ous effects.     Water  absorbs  very  little  of  it,  and   it  has  not 
been  condensed  into  a  liquid.     Twice  its   bulk   of  oxygen 
burns  it  completely,  with  a  loud    explosion,  forming  water 
and  an  equal  volume  of  carbonic  acid.     In  the  air  it  burns 
quietly  with  a  bright  yellow  flame,  giving  the  same  products. 
It  is  not  easily  decomposed  ;  but  at  a  red  heat,  in  a  porce- 
lain tube,  it  deposits  carbon   and  gives  out   hydrogen.     With 
moist  chlorine  in  the  sun-light,  it  forms  carbonic  and  hydro- 
chloric acids,  but  is  not  affected  by  it  in  the  dark. 

454.  Olefiant  Gas,  or  heavy  Citrbureled  Hydrogen  Gas. 
— This  gas  was  discovered  in  1796,  by  an  association  of 
Dutch  chemists,  who  gave  it  the  name  of  olefiant,  because  it 
forms  a  peculiar  oil-like  body  with   chlorine.     It  is  prepared 
by  mixing  strong  alcohol  with  five  or  six  times  its  weight  of 
oil  of  vitriol  in  a  capacious  retort,  and  applying  heat  to  the 
mixture.     The   action   is   complicated    and    cannot  be  well 
explained  at  this  time.     Ether  distils  over  soon  after  the  heat 
is  applied,  and  with  it,  the  olefiant  gas  which  may  be  collect- 
ed over  water.     The  alcohol  becomes  carbonized,  froths  up 
very  much,  and  carbonic  and  sulphurous  acids  are  given  off 

Give  the  reaction.  453.  What  is  the  density  and  composition  of 
this  gas  ?  Give  its  general  properties.  How  does  it  act  with 
chlorine.  454.  When,  and  by  whom,  was  olefiant  gas  discovered  1 
Whence  its  name  ?  How  is  it  prepared  ?  What  is  the  result  ? 


COMPOUNDS  OF  HYDROGEN.  265 

towards  the  close  of  the  process.  The  gas  can  be  purified  by 
passing  it  first  through  a  wash-bottle  containing  a  solution 
of  potash,  and  then  through  oil  of  vitriol ;  the  potash 
removes  the  acid  vapors,  and  the  oil  of  vitriol  retains  the 
ether. 

455.  Properties.  —  Olefiant  gas  is   a  neutral,  colorless, 
tasteless   gas,   nearly   inodorous,  and    having  a  density  of 
0-981,  100  cubic  inches   of  it  weighing  30-57  grains.     It 
burns  with  a  most  brilliant  white  light,  and  evolves  much  free 
carbon.     Its  splendid  combustion  makes  it  a  favorite  subject 
of  experiment.     With   an   equivalent   quantity   of  oxygen 
gas,  it  explodes  with  a  tremendous  detonation,  which  is  too 
severe  even  for  very  strong  glass  vessels.     Bubbles  of  the 
mixture  may  be  exploded   by  a  burning  paper,  as  they  rise 
from  beneath  the  surface  of  water.     It  is   decomposed   by 
passing  through  tubes  heated  to  redness,  -and  much  carbon  is 
deposited.     This  effect  happens  in  the  iron  retorts  of  city 
gas  Works,  in  which  crusts  of  pure  carbon,  sometimes  of 
great  thickness,  accumulate   from  the  decomposition  of  the 
gas. 

456.  As  already  remarked,  this  gas  forms  a  remarkable 
compound    with   chlorine  ;    the   gases   unite  (2  volumes  of 
chlorine  and  1  of  defiant)  by  simple  contact,  the  dense  oily 
liquid  collects  on   the  side  of  the  air-jar  and  surface  of  the 
water,  and   may  be  received  as  it  falls  in  a  basin  placed  for 
the  purpose  under  the  jar. 

If  two  measures  of  chlorine  and  one  of  olefiant  gas  be 
fired  as  soon  as  the  mixture  is  made,  by  a  candle,  or  lighted 
match,  from  the  open  mouth  of  the  jar,  the  hydrogen  of  the 
olefiant  unites  with  the  chlorine,  and  all  the  carbon  of  the 
former  is  set  free  in  a  dark  cloud,  filling  the  vessel. 

457.  Coal  gas  and  resin  gas  are  much   used  for  illumi- 
nating cities  ;  they  are  formed  chiefly  of  light  carbureted  hy- 
drogen and  olefiant  gas,  with  some  other  volatile  hydrocar- 
bons.    Their   illuminating   power   is   in    proportion   to   the 
amount  of  olefiant  gas  contained  in  the  mixture.     Numerous 
products  from  the  destructive  distillation  of  coal  and  resin 


455.  What  properties  has  olefiant  gas  ?  How  does  it  burn  ?  How 
does  it  act  with  oxygen  ?  How  is  it  decomposed  ?  What  happens 
in  large  gas  retorts  ?  456.  How  does  olefiant  gas  act  with  chlo- 
rine? If  the  mixture  is  at  once  fired,  how  does  it  act?  457.  For 
what  are  coal  and  resin  gases  used  ?  On  what  depends  their  illumi- 
nating power  ? 
23 


266  NON-METALLIC    ELEMENTS. 

require  to  be  removed  before  the  gas  is  fit  for  use.  It  is 
accordingly  washed  in  milk  of  lime  to  free  it  from  sulphu- 
reted  hydrogen  and  carbonic  acid,  and  sometimes  with  dilute 
sulphuric  acid  to  remove  ammonia.  Tar  and  soluble  oils  are 
condensed  by  passing  the  gas  through  a  series  of  iron  pipes 
in  water,  which  is  done  before  it  goes  to  the  lime  purifiers. 
The  gas  from  oil  has  a  higher  illuminating  power,  and  needs 
no  purification  when  well  prepared. 

A  natural  supply  of  coal  gas,  composed  of  light  carbureted 
hydrogen  and  defiant  gas,  is  used  to  illuminate  the  village  of 
Fredonia,  N.  Y.  ;  and  some  of  the  salt  works  in  Kenawha, 
Va.,  are  heated  by  the  burning  gas  conducted  for  the  purpose 
under  the  kettles.  Vast  volumes  of  this  gas  are  given  off 
from  the  Artesian  borings  in  those  regions. 

458.  Hydrogen  combines  with  boron,  forming  a  combus- 
tible gas,  which  bucns  with   the  green  flame  peculiar  to  the 
compounds  of  boron,  and  deposits  boracic  acid.     Its  compo- 
sition  and  properties  are   not   known.     From    analogy  we 
might  suspect  the  existence  of  a  series  of  borurets  of  hydro- 
gen, and  possibly  siliciurets  of  the  same  element. 

7.   Combustion  and  the  Structure  of  Flame. 

459.  Combustion  is  the  disengagement  of  light  and  heat, 
which  accompanies  chemical  combination.     Nearly  all  our 
operations  being  performed  in  presence  of  the  oxygen  of  the 
atmosphere,  the  term   combustion  has  come  to  be  restricted, 
in  a  popular  sense,  to  the  union  of  bodies  with  oxygen,  when 
heat  and  light  are  accompaniments  of  such  union. 

Combustible  bodies,  in  the  common  sense  of  the  term,  are 
those  which  burn  (i.  e.,  unite  with  oxygen  with  heat  and 
light)  under  ordinary  circumstances.  Thus,  carbon,  sulphur, 
and  phosphorus,  are  among  the  elementary  combustibles  ; 
and  tar,  oils,  wood,  &c.,  are  compound  combustibles. 
Oxygen  being  possessed  of  stronger  affinities  than  any  other 
elementary  body,  forms  compounds  with  those  bodies  which 
are  burned  in  it,  which  are  no  longer  combustible  ;  thus  iron 
which  has  been  burnt  (i.  e.  oxydized)  in  oxygen  gas,  (255,) 

How  are  they  purified  ?  What  natural  supplies  of  coal  gas  are 
named  ?  458.  What  compound  of  hydrogen  and  boron  is  named  ? 
459.  What  is  combustion  ?  What  popular  restriction  has  arisen  in 
the  use  of  this  term  ?  What  is  commonly  meant  by  combustible 
bodies?  What  is  said  of  bodies  which  have  been  burnt  in  oxygen  ? 


COMBUSTION    AND    FLAME.  267 

is  no  longer  capable  of  a  similar  change,  because  we  have 
no  other  body,  which,  at  common  temperatures,  can  remove 
the  oxygen  from  combination.  Iron  will  also  burn  brilliantly 
in  sulphur  vapor,  forming  a  compound,  (protosulphuret  of 
iron,)  which  is  incombustible  in  an  atmosphere  of  sulphur 
vapor,  but  which  will  still  burn  in  oxygen  gas.  This  is  only 
saying  that  the  affinities  (i.  e.  the  electro- negative  qualities) 
of  oxygen  are  more  powerful  than  those  of  sulphur. 

460.  The  division  of  elementary  bodies  into  combustibles 
and    supporters  of   combustion,  was    proposed    by    Doctor 
Thomson,  and  that  classification   has  prevailed  with  English 
and  American  authors  to  a  great  extent.     This   principle   is 
radically  defective  as  a  guide  to  any  philosophical   arrange- 
ment of  bodies,  since  it  seizes  on  a  single  phenomenon  ac- 
companying chemical  union,  and  disregards  most  of  those 
natural   analogies  which   group   the   elements   into  distinct 
classes. 

It  has  been  remarked  by  an  old  writer  on  chemistry,  that 
"  combustion  is  the  grand  phenomenon  of  chemistry."  It 
would  be  more  conformable  to  truth  to  say,  that  affinity  is 
the  grand  phenomenon  of  chemistry,  and  that  its  exertion  is 
sometimes  accompanied  by  the  evolution  of  heat  and  light. 

The  attentive  student  has  already,  it  is  hoped,  found 
sufficient  grounds,  in  the  arguments  and  illustrations  which 
have  been  presented,  to  admit  the  existence  of  a  higher 
chemical  philosophy  than  that  of  combustibles  and  sup- 
porters. 

461.  In  all  cases  of  combustion  the  action  is  reciprocal. 
Hydrogen  burns  in  common  air ;  but  if  a  stream  of  oxygen 
is  thrown  into  a  jar  of  hydrogen,  through  a  small  aperture  at 
the  top,  when  the  latter  is  burning,  the  flame  is  carried  down 
into  the  body  of  the  jar,  and  the  oxygen  will  continue  to 
burn  in  the  hydrogen,  as  it  issues   from   the  jet.      In  this 
case  the  oxygen  may  be  said  to  be  the  combustible,  and  the 
hydrogen    the   supporter.      The   simple   statement   in    both 
cases  is,  that  oxygen  and   hydrogen  combine  together,  and 
combustion — that  is,  the  disengagement  of  light  and  heat — 

Illustrate  this.  460.  What  is  said  of  the  division  of  bodies  into 
combustibles  and  supporters  of  combustion?  Why  is  this  principle 
of  classification  radically  deficient?  461.  What  is  said  of  the  re- 
ciprocal action  of  combustion  ?  Illustrate  this  by  a  jet  of  oxygen 
in  hydrogen  gas. 


268  NON-METALLIC    ELEMENTS. 

is  the  consequence.*  The  diamond  burns  in  oxygen  gas; 
but  the  latter  is  as  much  altered  by  the  union  as  the  former, 
and  we  cannot  therefore  say  whether  the  oxygen  or  the 
carbon  is  the  most  burnt.  Heat  and  light  attend  this  union  ; 
but  the  carbon  of  the  human  body  is  as  truly  burnt  in  the 
lungs  by  the  atmospheric  oxygen,  as  is  the  fuel  of  our  fires  ; 
and  the  product  of  the  combustion,  the  carbonic  acid 
thrown  out  by  the  lungs  at  every  exhalation,  is  the  same 
thing  which  is  discharged  at  the  mouth  of  a  furnace.  In  the 
case  of  the  animal  body,  the  combustion  is  so  slow  that  no 
light  is  evolved,  and  only  that  degree  of  heat  (98°  to  100°) 
which  is  essential  to  vitality.  We  cannot-  deny  that  there  is 
in  this  case  a  real  combustion,  and  yet  it  does  not  answer  to 
our  usual  definition,  since  no  light  is  evolved.  The  term 
combustion  must  have,  then,  a  chemical  sense  vastly  more 
comprehensive  than  its  popular  meaning.  The  rust  which 
slowly  corrodes  and  destroys  our  strongest  fixtures  of  iron, 
and  the  gradual  process  of  decay  which  reduces  all  structures 
of  wood  to  a  black  mould,  are  to  the  chemist  as  truly  cases 
of  combustion,  as  those  more  rapid  unions  with  oxygen 
which  arc  accompanied  by  the  splendid  evolution  of  light  and 
heat. 

462.  The  heat  produced  by  combustion  has  received  no 
satisfactory  explanation.     All  we  can  say  is,  that  any  change 
of  state  in  a  body  is  accompanied  by  an  alteration  of  tem- 
perature.    When   two  liquids   become  solid,  we  can   better 
understand  why  heat  should  be  produced,  (109.)     But  why 
the  union  of  carbon  and  oxygen,  to  form  a  gas,  should  evolve 
such  intense  heat  as  to  fuse  the   most  refractory  bodies,  is 
more  than  has  been  explained.     It  will   be  remembered  that 
chemical  combination  was  pointed  out  as  one  of  the  sources 
of  heat,  and  that  it  is  strictly  limited  to  the  amount  of  matter 
suffering  change. 

463.  The  temperature  at  which  bodies  become  luminous 
in  diffuse  daylight  is  considered   to  be  about  1000°.     Gases, 
however,  can  be  heated  much  higher  without  being  luminous  ; 

The  burning  of  the  diamond.  What  is  said  of  those  eases  where 
no  light  or  heat  accompanies  the  change?  462.  How  is  the  heat 
of  combustion  explained  ?  463.  At  what  temperature  do  bodies 
become  luminous  ?  How  is  it  with  gases  ? 

*  DanielPs  Introduction  to  Chemical  Philosophy,  p.  322. 


COMBUSTION    AND    FLAME.  269 

indeed,  it  is  probable  that  no  degree  of  heat  whatever  would 
make  common  air  or  any  other  gas  visible.  We  may  heat 
a  combustible  gas,  like  the  olefiant,  to  a  point  when  it  will 
take  fire  in  the  air.  This  we  do,  in  fact,  when  we  touch  it  with 
the  flame  of  a  candle.  The  current  of  heated  air  ascending 
from  an  argand  lamp  chimney  is  invisible ;  but  a  thin  wire 
held  in  it  will  at  once  glow  with  bright  redness,  showing  that 
the  air  is  highly  heated.  A  few  bodies,  when  intensely 
heated  in  the  air,  suffer  no  change  ;  such  are  gold,  platinum, 
palladium,  and  other  metals  not  easily  oxydized.  The  term 
incandescence  expresses  the  condition  of  such  bodies,  and 
varies  in  intensity  with  the  degree  of  heat.  A  white  heat  is 
considered  equal  to  about  3000°.  A  much  lower  temperature 
will  inflame  most  combustible  bodies,  and  the  combustion, 
when  once  begun,  is  continued  without  further  addition  of 
outward  heat,  as  is  seen  in  our  common  fires.  The  at- 
mosphere in  such  cases  supplies  all  that  is  required  to  con- 
tinue the  combustion. 

404.  The  structure  of  fame  deserves  our  particular 
attention.  Flame  is  ignited,  combustible,  aerial  matter. 
All  these  conditions  are  needed  to  constitute  flame,  as  a 
moment's  attention  will  show.  The 
flame  can  burn  only  in  contact 
with  the  air,  and  must  therefore 
consist  of  an  exterior  ring  or 
shell  of  flame,  and  an  interior 
cone  of  uninflamcd  combustible 
matter.  A  common  candle  or 
lamp  shows  those  conditions  per- 
fectly. The  wick  draws  up  the 
tallow  or  oil,  which  is  converted 
into  a  volatile  hydrocarbon,  as 
soon  as  it  touches  the  ignited 
portion  of  the  wick,  or  hot  atmosphere 

of  flame.  This  combustible  can  burn  only  in  contact  with 
oxygen ;  and  that  the  interior  portion  (a)  is  actually  inflam- 
mable gas,  is  very  easily  proved,  since  it  can  be  led  out  by 
a  small  glass  tube,  (&,)  and  set  fire  to  from  its  other  end. 

How  is  the  high  temperature  of  heated  air  made  evident  ?  How 
high  is  the  temperature  of  whiteness  ?  464.  What  is  flame  ?  How 
does  flame  burn  ?  Illustrate  this  in  the  case'of  the  common  candle. 
How  is  tha  interior  portion  seen  to  be  combustible  ? 

23* 


270 


NON-METALLIC    ELEMENT?. 


In  like  manner,  by  bringing  a  sheet  of  platinum  foil  over  the 
'flame  of  a  large  spirit-lamp,  it  will  be  heated  to  redness  in  a 
ring,  while  the  centre  will  remain  black,  showing  that  the 
interior  is  comparatively  cold,  and  the  exterior  intensely 
hot.  Phosphorus  may  be  placed  on  the  expanded  wick  of 
a  large  alcohol-lamp,  or  on  a  tuft  of  cotton  wet  with  alcohol, 
and  after  kindling,  it  can  be  at  once  extinguished,  by  setting 
fire  to  the  alcohol,  which,  rising  in  a  voluminous  flame, 
envelops  the  phosphorus  in  an  atmosphere  that  cannot 
sustain  its  combustion,  and  consequently  it  ceases  to  burn, 
but  commences  again  as  soon  as  the  air  comes  in  contact 
with  it. 

4ti5.  The  temperature  of  fame  is  much  higher  than  that 
of  ignited  solids,  even  when  the  color  of  the  flame  is  very 
feeble,  as  of  alcohol  or  pure  hydrogen.  The  quantity  of 
light  which  flames  emit  is  dependent  on  the  presence  of 
minute  particles  of  solid  matter,  which  glow  with  the  intense 
heat,  and  reflect  a  strong  light.  This  result  is  experienced 
when  the  flame  of  the  oxyhydrogen  blowpipe  falls  on  lime 
or  platina ;  and  the  brilliant  focus  of  the  galvanic  light  is 
probably  filled  with  the  vapor  of  volatilized  carbon,  or  of  the 
metals  suffering  combustion.  The  carbohydrogen  gases 
burn  with  such  intense  brilliancy,  on  account  of  the  minute 
particles  of  carbon  derived  from  the  decomposition  of  the  gas 
by  the  heat,  which  burn  in  the  air,  and  thus  give  the  strong 
light  peculiar  to  these  compounds.  \Vhon  the  particles  of 
free  carbon  become  too  numerous, 
and  there  is  not  oxygen  enough  to 
burn  them,  the  flame  smokes.  A 
common  tallow  candle  is  in  this  con- 
dition, and  is  therefore  a  very  im- 
perfect means  of  illumination.  The 
various  contrivances  in  common  use, 
as  argand  and  solar  lamps,  &c.,  have 
for  their  object  to  raise  the  temperature 
of  the  flame  so  high,  by  a  full  supply 
of  oxygen,  as  to  leave  no  carbon 


Illustrate  this  by  phosphorus.  465.  What  is  said  of  the  tempera- 
ture of  flame  (  On  what  does  the  luminousness  of  flame  depend  ' 
Illustrate  this.  When  the  free  carbon  becomes  too  abundant,  what 
happens  1  How  do  thp  argand  and  solar  burners  improve  the 
quality  of  flame 


COMBUSTION    AND    FLAME.  271 

unburnt.  The  quantity  of  light  thus  obtained  from  the  same 
quantity  of  oil  is  greatly  increased,  and  all  inconveniences 
from  smoke  and  bad  odors  avoided. 

The  common  laboratory  lamp  illustrates  this  principle,  as 
seen  in  the  sectional  figure.  It  will  be  observed  that  there  is 
a  central  opening  vertically  through  the  lamp,  which  allows 
a  column  of  air  to  draw  up  within  the  circular  wick,  and  the 
flame  is  thus  doubled,  as  compared  with  the  common  spirit- 
lamp,  or  candle. 

466.  The   student   who   resides    where   gas   is    used    for 

illumination,  possesses  a  ready  means  of 
procuring  a  very  powerful  and  economical 
heat,  which  he  can  command  at  pleasure, 
by  regulating  its  intensity  with  a  stop-cock. 
It  is  always  ready  and  can  be 
left  for  any  length  of  time. 
With  a  mica  chimney  and  a 
moveable  foot  connected  with  a 
flexible  gas-pipe,  the  gas-lamp 
may  be  placed  where  the  con- 
venience of  the  operator  re- 
quires. A  small  glass  spirit-lamp  with  a  close  cover  to  pre- 
vent evaporation,  is  an  indispensable  convenience  even  in  the 
humblest  laboratory. 

467.  Dr.  C.  T.  Jackson  has  contrived  a  modification  of 
the  common  argand   spirit-lamp,  which   is  the  most  powerful 
lamp-furnace  in   use.     This  invention  consists   in  applying 
the  principle  of  the  mouth-blowpipe  to  the  argand-lamp,  and 
is  accomplished   by  forcing  a  blast  of  air  or  of  pure  oxygen 
gas   from   a  bellows,  into  the  bottom  of  a  tube  within  that 
which  carries  the  circular  wick.     The  arrangement  is  such, 
that  the  blast  issues  in   a  narrow  ring  concentric  with  the 
wick  and  in  close  contact  with  it.     The  wick  is  turned  up 
pretty  high,  and  the  lower  orifice  of  the  argand  tube  stopped 
with  a  cork,  when  the  blast  is  in  use.     By  this  lamp  600 
grains  of  carbonate  of  soda  are  readily  fused  in  a  platinum 
crucible,  and   many  operations   accomplished  which   usually 
require  a  furnace  heat.     The  supply  of  air  or  gas  is  regula- 
ted by  a  screw  on  the  bottom  of  the  blast  tube,  and  the  bel- 
lows to  supply  the  blast  is  placed  beneath  the  table  and  worked 

What  is  the  principle  of  this  structure  ?  466.  What  is  the  gas- 
lamp  ?  467.  Describe  Dr.  Jackson's  lamp. 


272 


NON-METALLIC    ELEMENT?. 


convert   the 


by  the  foot.  If  the  intense  heat  is  not  wanted,  the  lower 
orifice  is  opened,  and  the  lamp  then  hecomes  only  a  power- 
ful argand.  The  chimney  of  this  lamp  must  be  made  of 
mica,  to  withstand  the  heat. 

468.  The  mouth-blowpipe  enables  us 
flame  of  a  corn- 
mon  candle  or 
lamp  into  a  pow- 
erful furnace.  By 
the  blast  from  the 
jet  of  the  blow- 
pipe, the  operator 
turns  the  flame  in 

a  horizontal  direction  upon  the  object  of 
experiment,  at  the  same  time  that  he  sup- 
plies to  the  interior  cone  of  combustible 
matter  a  further  quantity  of  oxygen.  The 
flame  suffers  a  remarkable  change  of 
appearance  as  soon  as  the  blast  strikes  it, 
and  the  inner  blue  point  has  very  different 
chemical  effects  from  the  exterior  or  yellow 
point.  Immediately  before  the  exterior 
flame  is  a  stream  of  intensely  heated  air, 
which  is  capable  of  powerfully  oxydizing  a 
body  held  in  it,  and  this  point  is  therefore 
called  the  oxydizing  fame.  The  inner  or 
blue  point  is  called  the  reducing  flame,  and  in  it  all  metallic 
oxyds  capable  of  reduction  are  easily  reduced  to  the  metallic 
state  or  a  lower  degree  of  oxydation.  Between  the  outer 
and  inner  flames  is  a  point  of  most  intense  heat,  where 
refractory  bodies  are  easily  melted.  Charcoal  is  generally 
employed  to  support  bodies  before  the  blowpipe  flame,  when 
we  would  heat  them  in  contact  with  carbon.  Forceps  of  pla- 
tinum are  used  to  hold  the  substance  when  it  is  to  be  heated 
alone  ;  and  a  small  wire  of  the  same  metal,  with  a  little 
loop  bent  on  one  end,  is  used  to  hold  a  globule  of  fused  car- 
bonate of  soda,  or  other  flux,  when  we  wish  to  submit  a  body 
to  the  action  of  such  reageants.  The  art  of  blowing  an  un- 
intermitting  stream  is  soon  acquired,  by  breathing  at  the  same 


468.  What  does  the  mouth-blowpipe  accomplish  ?.  Describe  the 
flame.  How  does  the  blast  affect  it  1  Distinguish  between  the 
reducing  and  the  oxydizing  flames. 


COMBUSTION    AND    FLAME.  273 

time  through  the  mouth  and  nostrils  ;  and  an  experienced 
operator  will  blow  a  long  time  without  fatigue.  No  instrument 
is  more  useful  to  the  chemist  and  mineralogist  than  the 
mouth-blowpipe.  By  its  means  we  may  in  a  few  moments 
submit  a  body  to  all  the  changes  of  heat,  or  the  action  of  rea- 
geants,  which  can  be  accomplished  with  a  powerful  furnace.* 
469.  The  temperature  of  flame  may  be  so  reduced  by 
bringing  cold  metallic  bodies  near  it  as 
to  be  extinguished.  On  this  simple 
fact  rests  the  power  of  the  "  safety 
lamp"  of  Sir  Humphrey  Davy  to  protect  the  life  of  the  miner. 
If  a  narrow  coil  of  copper  wire  be  brought  over  a  candle  or 
lamp  so  as  to  encircle  it,  the  flame  will  be  extinguished  ;  but 
if  the  wire  be  heated  previously  to  redness,  the  flame  con- 
tinues to  burn.  The  same  effect  will  be  produced  by  a  small 
metallic  tube.  A  wire  held  in  the  flame  is  seen  to  be  sur- 
rounded with  a  ring  of  non-luminous  matter.  If  many  wires, 
in  the  form  of  a  gauze,  are  brought  near  the  flame  of  a  can- 
dle, it  will  be  cut  off  and  extinguished  above  ;  only  a  current 
of  heated  air  and  smoke  will  be  seen  ascending,  while  the 
flame  continues  to  burn  beneath  and  heats  the  wire  gauze  red- 
hot  in  a  ring,  marking  the  limits  of  the  flame.  The  flame 
may  be  relighted  above  the  gauze,  -and  will  then  burn  as 
usual,  as  seen  in  the  second  figure.  Sir  Humphrey  Davy 
found  that  a  wire  gauze  would  in  all  cases  arrest  the  progress 
of  flame,  and  that  a  mix-  // . 

ture   of  explosive   gases  y)v 

could  not  be  fired  through 
it.  A  wire  gauze  is  only 
a  series  of  very  short 
square  tubes,  and  their 
power  to  arrest  flame 
comes  from  the  fact  that 


469.  How  do  cold  metallic  bodies  affect  flame  ?  What  valuable 
instrument  is  based  on  this  fact  ?  How  does  wire  gauze  affect  flames  ? 
What  may  the  wire  gauze  be  considered  ?  What  temperature  do  the 
carbohydrogens  require  for  their  combustion  ? 


*  The  student  would  do  well  to  consult  "  Berzelius  on  the  Blow- 
pipe," translated  by  J.  D.  Whitney.  Boston,  1845  ;  Ticknor  &  Co.  j 
12mo.  pp.  237, 


274 


NON-METALLIC    TLEMKNTS. 


they  cool  the  gases  below  their  point  of  ignition.  Providen- 
tially, the  heat  required  to  ignite  the  carbon  gases  is  much 
higher  than  that  which  will  produce  the  union  of  oxygen  and 
hvdrogen. 

470.  Safety  Lamp. — The  explosion  of  inflammable  gases 
in  coal  mines  has  destroyed  thousands  of  those  whose  duties 

required  them  to  submit  to  the  exposure.  To 
avoid  these  lamentable  accidents,  Davy  invented 
the  miner's  lamp,  which  is  only  a  common  lamp 
surrounded  by  a  cage  of  wire  gauze  completely 
enclosing  the  flame.  When  this  lamp  is  placed 
in  an  explosive  atmosphere,  the  gas  enters  the 
cage,  enlarges  the  flame  on  the  wick,  and  burns 
quietly,  the  gauze  effectually  preventing  the  pas- 
sage of  the  flame  outwards.  We  thus  enter  the 
camp  of  the  enemy,  disarm  him,  and  make  him 
labor  for  us.  The  miner  is  not  only  protected 
by  this  instrument,  but  is  rendered  conscious  of 
his  danger,  by  the  enlargement  of  his  flame. 
As  long  as  the  lamp  can  burn,  it  is  sale  to  stay, 
as  an  irrespirablc  atmosphere  would  extinguish 
the  flame.  The  powerful  blast  of  wind  which 
sometimes  sweeps  through  the  mines  may  render 
the  lamp  unsafe,  by  forcing  the  flame  against  the  gauze, 
until  it  is  heated  so  hot  as  to  inflame  the  external  atmosphere. 
This  accident  is  prevented  by  the  addition  of  a  glass  to  cover 
the  sides,  the  air  being  admitted  from  below  through  flat 
gauze  discs. 

471.  The  phenomena  of  the  safety  lamp  may  be  easily 
illustrated  by  the  teacher,  with  a  large  bell  glass  placed  over 
a  naked   lamp   and   left  open  beneath.     Hydrogen  may  be 
admitted  from  below  by  a  gas-pipe,  when  the  atmosphere  soon 
becomes    explosive  and   goes   ofT,    extinguishing   the    lamp. 
The   miners   lamp  under  the   same  circumstances,  will   first 
burn  with  an  enlarged  flame,  and  then  go  out  quietly,  as  soon 
as  the  air  can  no  longer  support  the  combustion. 


470.  For  what  use  was  the  miner's  lamp  contrived  ?  How  is  it 
constructed  ?  How  does  it  indicate  the  state  of  the  atmosphere  in 
the  mine?  471.  How  are  the  phenomena  of  the  safety  lamp  illus- 
trated ? 


METALLIC    ELEMENTS.  275 


II.  METALLIC  ELEMENTS. 


1.  General  Properties  of  Metals. 

472.  The  number  of  the  metallic  elements  is  about  forty-two, 
or  three  times  the  number  of  the  non-metallic  bodies,  which 
have  already  engaged  our  attention.     If  we  include  five  lately 
proposed  new  metals,  we  shall  have  forty-seven  bodies  in  this 
class.     Of  all  this  number,  however,  a  few  only  are  of  con- 
siderable interest,  while  many  (at  least  half)  are  totally  un- 
known in  common  life.     The  minerals  which  contain  several 
of  the  rare  metals,  in  combination  with  various  substances, 
are  among  the  most  uncommon  specimens  of  mineralogical 
cabinets. 

473.  A  metal  is  a  body  which  conducts  electricity  and 
heat,  which  is  opaque,  and   has  a  peculiar  brilliancy,  known 
as  the  metallic  lustre.     It  has  been  before   remarked  (251) 
that  metallic  lustre  is  the  only  property  which  belongs  pecu- 
liarly and  solely  to  this  class  of  bodies.     A  metal,  when 
submitted    in    solution  to   electrolysis,  is    always   given  out 
at  the  negative  side  of  the  battery,  and  is  therefore  a  positive 
electric.     Any  body  which  possesses  these  general  properties 
is  a  metal,  according  to  our  present  notions  of  the  metallic 
character.     We  see  every  variety  in  some  of  these  charac- 
ters.    Some  metals  are  almost  without  lustre,  as  manganese, 
whife  others,  like  gold  and   silver,  may  stand   as  examples 
of  perfection  in  this  as  well  as  in  all  other  metallic  properties. 
Opacity  is  not  complete  even  in  gold  and  mercury,  as  already 
mentioned,  (53.)     Some  metals  are  perfectly  malleable  when 
cold,  as  silver,  gold,  lead,  and  tin  ;  others  are  malleable  when 
hot,  as  iron,  platinum,  &c.,  and  are  not  without  this  property, 
though  in  a  less  degree,  even  when  cold.     Some,  like  zinc, 
are  larninable  at  a  moderate  heat,  but  brittle  above  and  below 
it ;  others,  like  antimony,  are  brittle  at  all  temperatures  short 
of  fusion.     We  have  already  explained  (18)  the  properties 
of  brittleness,  malleability,  ductility,  and  laminability.     The 
tenacity  of  metals  depends  much  on  their  relations  to  these 

472.  What  is  the  number  of  metallic  elements  ?  How  many  of 
these  are  of  much  importance  ?  473.  What  is  a  metal  ?  How  do 
they  act  in  electrolysis  ?  What  variety  is  seen  in  the  metallic 
character  ?  Is  opacity  perfect  in  them?  Mention  their  characters. 


276  METALLIC    ELEMENTS. 

properties.  Iron  is  an  example  of  great  tenacity  and  duc- 
tility, while  in  malleability  it  is  much  inferior  to  gold  and 
silver. 

474.  The  tenacity  of  metals  is  compared  by  using  wires 
of  the  same  size  of  different  metals,  and  ascertaining  how 
much  weight  they  will   sustain.     Iron  is  the  most  tenacious, 

and  lead  the  least.-    Wires  are  drawn   through 
*  *   smooth   conical    holes    in    a   steel    plate,    each 

succeeding  hole  being  a  little  less  than  its  pre- 
decessor. In  this  way  wires  of  extreme  fine- 
ness may  be  drawn  from  several  of  the  ductile 
metals.  Dr.  Wollaston  succeeded,  by  a  pecu- 
\  .*  liar  method,  in  making  a  gold  wire  so  small 
^-'  that  530  feet  of  it  weighed  only  one  grain ;  it 
was  only  y^TT  °^*  an  mch  m  diameter;  and  a  platinum  wire 
was  made  by  the  same  philosopher,  of  not  more  than  -j^^ 
of  an  inch.  Metals  passed  repeatedly  through  the  rolling- 
mill,  or  wire  plate,  become  stiff  and  brittle,  but  are  again 
made  soft  by  heating  them  to  redness  and  cooling  them 
slowly.  This  is  called  annealing.  Copper  is  annealed  by 
plunging  the  red-hot  metal  into  cold  water,  while  the  same 
treatment  renders  iron  and  steel  extremely  hard. 

475.  The  fusibility  and  density  of  metals  differ  very 
much.     Platinum  is  at  once  the   most  dense  of  all   bodies, 
being  21  to  21 -5,  and  also  one  of  the  most  infusible.     Gold 
is  next  in  density,  (19-26,)  but  fuses  at  2016°  F.     Palladium, 
uranium,    cobalt,    nickel,    iron,    molybdenum,    manganese, 
colurnbium,   tungsten,  and  titanium,  are  all   infusible   below 
3000°,    (the    heat  of  the  most   powerful  air  furnace ;    and 
most  of  these  are  altogether  infusible.     In  density,  sodium 
and   potassium  occupy  the  lowest  points,  (-972  and  -865,) 
being  less   in  density  than  water,  and  they  also  fuse  at  the 
low  temperature  of  190°  and  136.° 

476.  Metals  vary  also  in  volatility  as  much  as  in  other 
properties.     Mercury   boils  at  662°,  and   arsenic,  tellurium, 
cadmium,  zinc,  potassium,  and  sodium,  are  also  volatile  at 


474.  How  is  the  tenacity  of  metals  compared  ?  Explain  the  use 
of  the  wire  plate.  How  fine  have  wires  of  gold  and  platinum  been 
made?  What  is  annealing?  How  is  it  accomplished  in  different 
metals  ?  475.  How  do  the  density  and  fusibility  of  metals  com- 
pare ?  476.  How  do  metals  compare  in  volatility  by  heat  ? 
Mention  some  of  the  volatile  ones. 


GENERAL  PROPERTIES  OF  METALS.          277 

temperatures  below  a  red  heat.  It  is  not  impossible  that  all 
the  metals  would  be  volatile,  if  we  could  heat  them  highly 
enough ;  but  many  of  them,  as  gold,  platinum,  silver,  &c., 
may  be  exposed  to  the  highest  heat  of  a  wind-furnace  with- 
out change.  Some  metals  assume  a  semi-fluid  or  pasty  con- 
dition before  melting,  such  as  platinum  and  iron,  both  of 
which  can  be  welded  or  made  to  unite  without  solder,  when 
in  this  soft  state  ;  lead,  potassium,  and  sodium,  can  be 
welded  in  the  cold,  as  also  can  mercury,  when  it  is  frozen. 
In  cooling  from  fusion,  some  metals  crystallize  beautifully, 
of  which  bismuth  is  an  example,  while  others,  as  gold  and 
platina,  are  not  commonly  seen  in  the  crystalline  form. 

477.  The  metals  are  rarely  found  in  their  metallic  state 
in    nature.     Their  characters  are  generally  masked    under 
some  form  of  combination  with  oxygen  or  sulphur.     Thus, 
iron  is   perhaps   never  seen  in  a  malleable   form   in   mines. 
The  masses  of  malleable  iron   found   on  the  surface  of  the 
earth    are   probably   all   of  meteoric   origin,    having   fallen 
through  the  atmosphere  to  the  earth.     Some  metals,  as  gold, 
silver,  platinum,   copper,    bismuth,    and    a   few  others,   are 
frequently  found  native,  or  in  the  malleable  form,  either  pure 
or  alloyed  with  each  other.     An  alloy  is  the  union  of  two 
metals,  as  of  copper  an<l   zinc,  to  form   brass,  and   lead  and 
tin,  to   make  pewter,  &c.     Gold   is   usually  found   alloyed 
with  silver,  and  platinum  has  generally  several  rare  metals 
alloyed  with  it.     Alloys  are   feeble  chemical   combinations, 
and  are  usually  best  suited  to  artificial   purposes  when  made 
in  the  atomic  proportions  of  the  several  metals.     The  alloys 
of  mercury  are  called  amalgams.     Copper  and  tin  unite  in 
several  distinct  proportions,  forming  very  unlike  alloys,  as 
gun  and  bell-metal,  and   speculum-metal.     Several   distinct 
compounds  of  gold  with  silver,  and  also  of  other  metals, 
have  been  recognised. 

478.  In  their  chemical  relations   the  metals  are  highly 
electro-positive,  and  form  compounds  with  all  the  members  of 
the  oxygen  group,  and  v/ith  phosphorus,  carbon,  dec.     They 


What  is  said  of  the  possible  volatility  of  others  ?  On  what  pro- 
perty does  welding  depend  ?  What  of  the  crystallization  of  metals  ? 
477.  In  what  state  do  the  metals  occur  in  nature  ?  With  what  are 
they  generally  combined?  Which  are  frequently  in  a  metajlic 
state  ?  What  are  alloys  ?  Are  they  in  atomic  proportions  ?  What 
are  the  alloys  of  mercury  called  ?  478.  In  their  chemical  relations 
the  metals  are  what? 
24 


278  METALLIC    ELEMENTS. 

all  unite  with  oxygen,  and  usually  in  more  than  one  propor- 
tion, but  their  affinity  for  this  element  is  very  various.  The 
majority  of  metals  will  combine  slowly  with  the  oxygen  of 
the  air,  forming  a  coating  of  oxyd,  (or  rust,)  which  usually 
protects  the  metal  from  further  action.  This  is  the  case 
with  lead,  zinc,  copper,  and  iron.  Sodium  and  potassium, 
and  the  metals  of  the  alkalies  generally,  nave  so  strong  an 
affinity  for  oxygen  as  to  be  able  even  to  decompose  water  at 
all  temperatures. 

479.  The  oxyds  of  the  metals  may  be  divided  into  three 
classes.     1st,  the  protoxyds,  which  are  strongly  basic  ;    2d, 
neutral,  or  those  which  are  neither  basic  nor  acid  ;  3d,  those 
which  are  decidedly  acid  in  their  relations.     The  changes 
of  character  in  oxyds,  have  a  uniform  relation  to  the  amount 
of  oxygen  they  contain,  the  higher  oxyds  being  either  neutral 
or  decidedly  acid.     Thus   the   protoxyd  of  manganese  is  a 
strong    base,  the    deutoxyd  is  feebly  basic,  the  peroxyd   is 
indiiferent,  and  the  higher  oxyds  are  the  manganic  and  per- 
manganic acids  ;  which  are   capable   of  replacing  sulphuric 
and    hy perchloric    acids.     Arsenic   and    antimony  have  no 
protoxyds,  and  are  remarkable  for  forming  strong  acids  with 
oxygen,  (250,  CLASS  IV.)     By  this  feature  they  arc  closely 
assimilated,  as  has  already  been  remarked,  to  the  non-metallic 
bodies. 

480.  The  compounds  which  the  metals  form  with  chlorine ', 
iodine,  sulphur,  &c.,  bear  a  very  striking  analogy  in  compo- 
sition to  the  oxyds  of  the  same  metals.     So  true  is  this,  that 
knowing  what  oxyds  a  given   metal  forms,  we  can  almost 
certainly  tell  what  the  composition  of  its  sulphurets,  chlorids, 
&c.,  will  be.     Thus  the  oxyds  of  iron  being  FeO  and  Fe02O3, 
we  find  that  the  sulphurets  of  the  same  metal  are  FeS  and  Fo2S3, 
and  the  chlorids  FeCl  and  Fe2Cl3.     It  might  be  inferred  from 
this  statement,  that  where  these  metallic  bodies   unite  with 
acids    to    form  salts,  there  would  be  the   same   conformity 
among  them  that  is   found   among  their  bases,  and  such  we 
shall  find  to  be  the  fact. 


What  is  their  affinity  for  oxygen?  479.  How  are  the  oxyds 
divided  ?  What  characters  have  these  three  classess  ?  On  what 
does  this  character  depend?  Illustrate  this  in  the  case  of  manga- 
nese. What  metals  are  remarkable  for  forming  acids  ?  To  what 
are  they  thus  assimilated  ?  480.  To  what  are  the  metallic  chlorids 
analogous?  Illustrate  this.  What  inferences  regarding  the  saline 
compounds  of  those  bodies  ! 


GENERAL  PROPERTIES  OF  METALS.          279 

481.  Combinations  of  the  metallic  oxyds,  chlorids,  sul- 
phurets,  &c.,  take  place  always  among  members  of  the  same 
series,  that  is,  oxyds  with  oxyds,  chlorids  with  chlorids,  sul- 
phurets  with  sulphurets,  and  so  on :  those  members  of  the 
same  series  which    differ   greatly  in  character   being    most 
disposed    to   unite,  as    the  oxygen   acids    with    the   oxygen 
bases,  &c.     Thus,  sulphuric  acid  (a  powerful  oxygen  acid) 
and  protoxyd  of  iron  (a  powerful  oxygen  base)  unite  to  form 
a  salt  which  is  entirely  neutral,  and  in  which  the  properties 
of    neither   constituent    are    sensible,    having    the    formula 
FeO,  SO3  for  the  dry  sulphate  of  iron. 

482.  Compounds  which    belong   to   unlike   or   different 
series,  on  the  contrary  do  not  unite,  but  often  mutually  de- 
compose  each   other.     Thus,  when   hydrochloric  acid  and 
potash  are  brought  together,  both  are  decomposed,  water  and 
chlorid  of  potassium  being  formed,  as  may  be  understood 
from  the  following  symbols  : 

Potash.    Hydrochloric  acid.    Water.     Chlorid  of  Potassium. 
KO     +     HC1        =      HO      -f      KC1 

The  latter  remains   in   solution,   and   may  be   obtained   in 
crystals  on  evaporation. 

483.  When  any  base  unites  with  an  acid  to  form  a  neu- 
tral salt,  there  must  be  as  many  equivalents  of  acid  em- 
ployed, as  there  are  of  oxygen  in  the  base  itself.     The  same 
is  true  also  of  those  acids  which   contain   no  oxygen,  as  the 
hydrochloric,  provided  the  metallic  oxyd  dissolves  in  hydro- 
chloric acid  without  the  evolution  of  chlorine.     For  example, 
peroxyd   of   iron    dissolved    in   hydrochloric  acid   produces 
water  and  a  perchlorid  of  iron :  3HC1  and  Fe2O3  giving  rise 
to  3HO  and  Fe2Cl3. 

484.  Theory  of  Salts. — The  binary  compounds  of  chlo- 
rine, iodine,  &c.,  with  many  of  the  metals,  particularly  those 
of  the  alkaline  class,  have  in  an  eminent  degree  the  properties 
of  salts,  and   among   them    we   recognise   particularly  the 


481.  How  do  combinations  among  metallic  oxyds,  &c.,  take 
place  ?  Illustrate  this  by  sulphuric  acid  and  protoxyd  of  iron.  482. 
Compounds  which  belong  to  different  series  act  how  ?  Illustrate 
this  by  potash  and  hydrochloric  acid.  483.  What  condition  of  neu- 
trality is  here  stated  in  the  formation  of  salts  ?  How  in  case  of 
hydrochloric  acid  ?  Illustrate  this  in  case  of  peroxyd  of  iron  and 
HC1.  484.  What  are  the  binary  compounds  of  the  oxygen  group 
like? 


280  METALLIC    ELEMENTS. 

chlorid  of  sodium  or  common  salt,  which  is  the  parent,  it 
may  be  said,  of  all  salts,  or  that  body  from  which  they  arc 
all  named.  If  the  old  definition  of  a  salt,  however,  be  ad- 
mitted, those  bodies  cannot  be  called  salts,  since  according 
to  that  view  a  salt  is  a  compound  of  the  oxyd  of  a  metal  with 
an  oxygen  acid.  To  avoid  this  difficulty,  two  classes  of 
salts  have  been  instituted,  the  first  of  which  includes  all 
those  binary  compounds  which,  like  common  salt,  have  a 
metallic  base  in  direct  union  with  a  salt-radical  ;  and  the 
second  includes  those  salts  which,  like  sulphate  of  soda,  are 
supposed  to  be  constituted  of  the  oxyd  of  the  metal  and  an 
oxygen  acid.  The  first  have  been  called  the  haloid*  salts, 
and  the  second  the  oxy-salts. 

485.  The  term  "  salt-radical"  just  employed,  includes 
not  only  all  the  members  of  the  oxygen  group,  except  oxy- 
gen itself,  but  also  all  those  compound  bodies  which,  like 
cyanogen,  and  numerous  similar  substances,  act  the  part  of 
elements  in  the  formation  of  compounds. 

In  stating  the  constitution  of  sulphuric  acid,  (294,)  it  will 
be  remembered  that  the  expression  SO4  +  H  was  employed  as 
an  equivalent  to  SOg-fHO.  It  is  claimed  that  all  the  hydra- 
ted  acids  arc  in  reality  compounds  of  hydrogen  with  a  simi- 
lar radical,  and  accordingly  nitric  acid  will  be  NO6-f  H, 
instead  of  NO5  +  HO.  One  principal  objection  to  this  view 
is,  that  these  hypothetical  radicals  have  never  been  isolated. 
But  the  same  is  true  of  NO5,  which  is  entirely  an  unknown 
body,  and  so  are  nearly  all  the  organic  acids,  independently 
of  water  or  hydrogen.  Moreover,  those  acids  which  are  capa- 
ble of  existing  dry  and  in  a  separate  state,  as  sulphuric,  (SO3,) 
phosphoric,  (PO5,)  and  carbonic,  (CO2,)  are  not  acids  as  long 
as  they  remain  dry,  and  although  they  form  compounds  with 
dry  ammonia,  these  compounds  are  not  salts.  Sir  Hum- 
phrey Davy  long  ago  proposed  to  consider  hydrogen  as  the 
real  acidifying  principle  in  all  acids.  This  view  of  the  case 
is  therefore  by  no  means  new.  What  we  now  know  of  the 


What  is  the  definition  of  a  salt  ?  What  two  classes  of  salts  have 
been  instituted  to  meet  this  difficulty  ?  485.  What  bodies  are  in- 
cluded under  the  term  salt-radical?  What  is  the  salt-radical  view 
of  the  composition  of  sulphuric  acid  ?  State  the  objections  against, 
and  reasons  for  this  view. 


From  halsy  sea-salt,  and  eidos,  in  the  likeness  of. 


GENERAL  PROPERTIES  OF  METALS.          281 

metallic  character  of  hydrogen,  goes  to  confirm  his  theory. 
If  the  salt-radical  theory  is  to  be  adopted,  all  acids  will  be 
considered  as  hydrogen  acids,  and  all  salts  as  haloid  salts. 
For  example,  let  us  take  two  common  saline  bodies  and  pre- 
sent them  according  to  these  two  views.* 

Old  view.  New  view. 

Sulphate  of  zinc,  ZnO  -f  S03  Zn  -f  SO4 

Nitrate  of  soda,  NaO-t-N05  Na  +  N06 

486.  According  to  the  new  view,  when  an  acid  dissolves 
a  metal,  there  is  no  necessity  for  supposing  water  to  be  de- 
composed.    The  metal  takes  the  place  of  the  hydrogen,  and 
the  latter  is  given  off  in  a  gaseous  form  ;  or  if  the  oxyd  of 
the  metal  is  used,  the  oxygen  and  hydrogen  unite  to  form  water, 
and  no  effervescence  ensues.     We  shall  consider  the  saline 
compounds  of  the  metals  under  each,  and  not  devote  a  sepa- 
rate part  of  the  work  to  their  discussion.     The  nomenclature 
of  the  salts  has  already  been  explained,  (201,)  and  need  not 
be  repeated  here.  * 

2.  Classification  of  Metals. 

487.  Until  we   are  more  familiar  than  we  now  are,  with 
all  the  principles  of  isomorphism,  with  the  constitution  of 
many    metallic   oxyds,  sulphurets,  &c.,    and    the    relations 
which  the  study  of  organic  chemistry   is  constantly  unfold- 
ing, it  will  not  be  found  easy  to  name  an  unexceptionable  class- 
ification for  the  metallic    bodies.     The  order  in  which  the 
metals  are  discussed  in  the  following  pages,  does  not  differ 
materially  from  that  generally  followed  in  elementary  works, 
and  it  is  presumed  that  it  will  be  found  well  adapted  to  the 
purposes  of  the  general  student. 


Give  the  constitution  of  sulphate  of  zinc  and  nitrate  of  soda  on 
The  old  and  new  views.  486.  How  according  to  the  new  view,  do 
metals  and  oxyds  dissolve  in  acids  ?  487.  What  is  said  of  the 
classification  of  the  metals  ?  What  classification  is  followed  here  ? 


*  It  is  impossible  to  do  justice  to  the  new  theory  of  salts  in  so 
limited  a  space  as  we  allot  ourselves,  and  the  reader  who  wishes  to 
seek  further  information,  is  referred  to  Mr.  Graham's  Elements  of 
Chemistry,  p.  158,  English  edition  This  view  has  been  strongly 
controverted,  and  is  frequently  rejected.  In  this  country  it  has  been 
ably  contested  by  Dr.  Hare.  Sec  Am.  Jour.  Science,  vol.  i.  2d 
series,  p.  82.  377. 


282  METALLIC    ELEMENTS. 

CLASS  I.     METALS  OF  THE  ALKALIES. 

15.    POTASSIUM. 

Equivalent,  39-19.     Symbol,  K.  (Kalimn.)     Density,  -865. 

488.  History. — Potassium  was  discovered  by  Sir  Hum- 
phrey Davy  in  1807;  at   the  same  time  with  its  congeners, 
sodium,  barium,  strontium,  and   calcium.     Before   that   time 
the  alkalies  and  alkaline  earths  were   looked  upon  as  simple 
elementary  bodies,  and  were  so  treated  in  all  chemical  works. 
Davy  found  that  on  passing  the  electric  current  from  a  pow- 
erful  voltaic  battery,  through  a  cake  of  moistened  potash, 
both  electrodes  being  of  platinum,  violent  action   followed, 
oxygen  was  evolved  with  effervescence  at  the  positive  pole, 
and   bright  metallic  globules,  like  mercury,  accompanied  by 
hydrogen  gas,  appeared  at  the  negative  pole.     Some  of  these 
globules  flasjied  and  burnt  with  a  violent  light  as  they  reached 
the  air,  and  others  remained  and  were  soon  covered  with  a 
white  film  that  formed  on  their  surfaces.     These    globules 
were  the   metal  potassium,  and  its  discovery  constitutes  one 
of  the  most  interesting  chapters  in  chemical  history. 

Potassium  in  combination,  chiefly  as  silicate  of  potash,  is 
widely  diffused  over  the  globe.  It  forms  a  part  of  all  fertile 
soils,  and  the  chief  source  from  which  it  is  artificially  pro- 
cured is  the  ashes  of  hard-wooded  forest-trees,  which  derive 
it  from  the  soil  on  which  they  grow.  It  is  also  present  in 
sea-water,  as  chlorid  of  potassium,  and  is  found  in  the  ashes 
of  sea-plants. 

489.  Preparation.  —  The    expensive    and    troublesome 
method    of  procuring   this    metal    by   galvanism    has   been 
replaced  by  a  much  more  convenient  and  productive  furnace 
operation,  founded  on  the  decomposition  of  potash  at  a  white 
heat  by  charcoal.     For  this  purpose  carbonate  of  potash  is 
intimately  mixed  with  charcoal,  which  is  best  prepared  by 
igniting  cream  of  tartar  in  a  covered  crucible,  which  yields  a 
black   mass  commonly  known   as  black  flux,  consisting  of 
carbonate  of  potassa,  and  charcoal  derived  from  the  organic 
acid.     This  mass  is  finely  powdered,  and  one-tenth  part  of 

488.  What  is  the  symbol  and  equivalent  of  potassium  ?  When, 
and  by  whom,  and  how  was  it  discovered  ?  How  is  this  metal 
found  in  nature  ?  489.  How  is  potassium  prepared  ? 


POTASSIUM.  283 

charcoal  in  small  lumps  being  added  to  it,  the  whole  is  trans- 
ferred to  an  iron  retort,  formed  of  a  quicksilver  bottle,  and 
laid  horizontally  in  a  powerful  wind  furnace.  A  short  iron 
tube  connects  the  iron  bottle  with  a  copper  vessel  of  peculiar 
construction,  containing  naphtha,  and  kept  cold.  The  bottle  is 
then  gradually  raised  to  an  intense  heat,  having  been  pre- 
viously protected  by  a  well-dried  coating  of  sand-luting  to 
guard  the  iron  against  fusion.  Decomposition  of  the  carbon- 
ate of  potash  follows,  carbonic  oxyd  gas  escapes,  and  metal- 
lic potassium  distils  over  in  melted  globules,  which  fall  into 
the  naphtha,  where  they  are  preserved.  Many  precautions 
are  required  to  insure  success,  and  particularly  to  see  that 
the  tube  of  delivery  does  not  become  stopped  ;  to  guard 
against  which,  the  apparatus  is  so  constructed  that  a  strong 
iron  rod  can  be  thrust  in  to  clear  the  opening. 

The  first  product  is  not  pure,  and  must  be  redistilled  in  a 
small  iron  retort,  with  a  little  naphtha,  into  a  receiver  con- 
taining that  liquid.  It  is  requisite  to  employ  naphtha  in  this 
process,  because  it  contains  no  oxygen  in  its  constitution,  and 
does  not  readily  suffer  change  from  the  action  of  potassium. 

490.  Properties. — Potassium,  when  recently  obtained,  is 
a  brilliant,  silver  white  metal,  possessing  the  metallic  lustre 
in  an  eminent  degree.  At  common  temperatures  it  is  soft 
like  putty,  and  may  be  easily  moulded  or  welded  by  the 
fingers.  It  is  the  lightest  metal  known,  having  a  density  of 
only  '865  ;  consequently  it  floats  on  water,  for  the  oxygen  of 
which  it  has  so  great  an  affinity  as  to  decompose  it  at  all 
temperatures.  It  burns  brilliantly  on  the  surface  of  tho 
water  with  a  beautiful  violet  purple  flame,  and  is  rapidly 
propelled  over  its  surface  by  the  gases  and  vapors  evolved 
in  the  combustion,  forming  one  of  the  most  attractive  of  chem- 
ical experiments.  The  hydrogen  of  the  decomposed  water 
also  burns  at  the  same  time.  Any  considerable  quantity 
thrown  on  water  will  explode  violently,  scattering  the  burning 
metal  in  all  directions.  Exposed  to  the  dry  air,  it  soon 
tarnishes,  and  gradually  falls  to  a  white  powder,  (potash.) 
Its  metallic  lustre  may  be  beautifully  seen  by  melting  it 
under  naphtha,  when  it  is  extremely  brilliant.  At  30°  it  is 
brittle  and  crystallizes  in  cubes  ;  at  150°  it  melts,  and  below 


Describe  the  arrangement.  How  is  the  metal  preserved  ?  490. 
Give  its  density.  What  is  its  strongest  affinity  ?  What  is  its  action 
on  water  ?  How  does  air  affect  it  ?  How  does  heat  affect  it  ? 


284  METALLIC    ELEMENTS. 

redness  it  boils  and  is  raised  in  vapor.     It  may  be  distilled 
unchanged,  in  vessels  free  from  oxygen. 

491.  The  uses  of  potassium  are  purely  scientific.     It  is  a 
most  powerful  means  of  research,  since  its  affinity  for  oxy- 
gen is  so  great  as  to  enable  it  to  decompose  the  chlorids  of 
aluminium,  glucinum,  yttrium,  thorium,  magnesium,  and  zir- 
conium, yielding  to  us  the  metallic  bases  of  these  compounds. 
It  is  also,  as  will  be  remembered,  (356  and  368,)  the  means 
by  which  silicon  and  boron  are  obtained. 

1.  Compounds  of  Potassium. 

492.  Potassium  combines  with  all  the   members  of  the 
first  three  classes,  forming  bodies   several   of  which  are  of 
great  importance  in  the  arts  and  in  pharmacy.     We  can  de- 
scribe only  a  few  of  the  most  important  of  these  compounds. 

493.  The    Oxyd   of    Potassium    is    formed    only    when 
potassium  is  exposed  to  dry  oxygen  or  common  air.     It  is  a 
white  powder,  strongly  alkaline,  which   has  a  great  affinity 
for  water,  forming  with  it  three  distinct  hydrates,  the  first  of 
which  is  caustic  potash,  (KO,HO.)      This    hydrate  is  a 
white  solid,  which   fuses  at  a  temperature  near  to  redness ; 
but  no  degree  of  heat  will  expel  the  equivalent  of  water  with 
which   it   is  combined.     On    cooling,  it   forms  a  somewhat 
crystalline,   compact   mass,  which    has  a  great  avidity   for 
water,  attracting  it   rapidly  from  the  atmosphere.     Half  its 
weight  of  water  will  dissolve  it,  and   it   is   also   soluble   in 
alcohol.     It  is  best  prepared  by  decomposing  pure  carbonate 
of  potash,  dissolved  in   10   parts  of  water  in  a  clean   iron 
vessel,  with   half  its  weight  of  good   quick-lime,   previously 
slaked   and   mingled  with   so  much  water  as  to  form  a  thin 
paste,  called  milk  of  lime.     This  is  added  in  small   portions 
to  the   potash   solution  while  the  latter  is   boiling,  a  short 
interval    being  allowed   between  each  addition ;  all  the  lime 
being  added,  the  whole  is  boiled  for  a  few  minutes,  and   then 
is  removed  from  the  fire  and  covered  up.     Care  is  needed  to 
keep  the  solution  dilute,  to  prevent  the  caustic  potash  formed 
from  decomposing  the  resulting  carbonate  of  lime.     After 

491.  What  are  its  uses  ?  What  other  bodies  have  been  produced 
by  its  means  ?  492.  Name  the  compounds  of  potassium  with  the 
oxygen  group.  493.  How  is  its  oxyd  formed  ?  What  is  its  hydrated 
oxyd  called  ?  What  are  the  properties  of  the  hydrate  of  potash  ? 
How  is  it  prepared  ? 


COMPOUNDS    OF    POTASSIUM.  285 

standing  a  few  hours,  until  all  the  lime  has  settled  and  the 
liquid  is  clear,  it  is  drawn  off  by  a  syphon,  and  concentrated 
by  boiling  in  a  clean  iron  pan  or  silver  capsule,  until  it  has 
an  oily  consistence,  when  it  is  poured  out  upon  a  clean 
surface  of  iron  or  marble;  it  then  hardens  into  the  white 
solid  hydrate  called  caustic  potash.  To  insure  its  purity,  it 
may  be  dissolved  in  absolute  alcohol,  which  will  leave 
behind  its  impurities.  The  alcohol  is  expelled  from  the 
decanted  solution  by  heat,  and  the  solid  potash  recovered  by 
fusion  in  a  silver  crucible.  The  moderately  strong  solution 
of  potash  answers  most  of  the  purposes  of  the  laboratory  as 
well  as  the  solid  hydrate. 

494.  The  solution  of  caustic  potash  is  intensely  alkaline, 
saturates    the   most   powerful   acids,  restores  the  colors  of 
reddened  vegetable  blues,  and  turns  many  of  them  green ; 
it  has  an  acrid  and  most  disgusting  taste,  peculiar  to  alkalies, 
and,  when  strong,  attacks  all  organic  matters,  dissolving  and 
disorganizing  them.     Its  solution  feels  soapy  on  the  fingers, 
and  forms  compounds  with  fats,  called  soaps.       The  solid 
potash  is  often  used  as  a  caustic  by  surgeons,  whence  its 
name.     Silica  is  dissolved  by  it.     Its  solution  absorbs  car- 
bonic acid  perfectly,  and   is  employed  for  that  purpose   in 
organic   analysis  ;    the  solid  potash  removes  both  carbonic 
acid  and  moisture  from  the  air,  and   is  therefore  sometimes 
used  in  desiccation. 

495.  The  presence   of  potash   in  solution  may  be  de- 
tected  by  an   alcoholic  solution  of  the  chlorid  of  platinum, 
which  throws   down   a   yellow  crystalline   precipitate   in  a 
concentrated  solution.      Perchloric,  tartaric,  and  hydrofluo- 
silicic  acids,  are  also  tests   of  the  presence  of  potash,  which 
forms  with  all  of  them  precipitates  but  little  soluble  in  water. 

496.  Peroxyd  of  Potassium  is  an  orange-yellow  powder, 
formed  by  passing  oxygen   over  potash   heated  to  redness  in 
a  tube.     It  is  decomposed   by  water,  oxygen  being  given  off, 
and  a  solution  of  potash  remaining. 

497.  Chlorid  of  Potassium  may  be  formed  by  the  direct 
combustion  of  potassium  in  chlorine  gas,  which  takes  place 


To  insure  its  entire  purity,  how  is  it  treated  ?  494.  What  are 
the  properties  of  its  solution  ?  What  compounds  does  it  form  with 
fats  ?  Why  is  it  called  caustic  ?  Name  some  of  its  other  uses  and 
properties.  495.  How  is  its  presence  detected  ?  496.  Peroxyd  of 
potassium  is  how  prepared  ?  497.  How  is  the  chlorid  made,  and 
what  are  its  properties  ? 


286  METALLIC    ELEMENTS. 

spontaneously.  It  is  also  formed  by  dissolving  potash  in 
dilute  hydrochloric  acid  to  saturation,  when  cubic  crystals  of 
chlorid  of  potassium  are  obtained  on  evaporating  the  solution. 
It  is  also  left  as  a  residuum  after  the  oxygen  process,  (253.) 
It  has  a  bitter  saline  taste,  and  does  not  preserve  meats,  like 
the  chlorid  of  sodium. 

498.  Bromid  of  Potassium  is   prepared   by  saturating  a 
solution  of  potash  with  bromine,  evaporating  the  solution  and 
igniting  the  residuum  in  a  covered   crucible  of  platinum  or 
iron.     The  melted   mass  is   bromid  of  potassium,  and  may 
be  turned  out  to  cool  on  an  iron  plate.     In  the  solution,  both 
bromate  of  potash  and   bromid   of  potassium   exist,  but  the 
ignition  expels  oxygon,  and  only  the  bromid  is  left.     It  is  a 
white  soluble  salt,  which  crystallizes  in  cubes,  and  is  soluble 
in   alcohol.     The   crystals    are  anhydrous,  and   decrepitate 
when   heated,  like  common   salt.     Bromid  of  potassium  is 
frequently  found  in  the  waters  of  saline  springs  and  inland 
seas. 

499.  lodid  of  Potassium,  formerly  called  hydriodate  of 
potash,  is  a  compound  of  great  use   in   medicine,  being  the 
form  in  which   iodine  is  usually  employed   in  medical  prac- 
tice.      It    is   obtained    by    a    process    similar   to   that    just 
described  for  the  bromid,  and  also  by  decomposing  the  iodid 
of  iron,  by  a  solution  of  potash.     It  is  a  white  salt  in  cubic 
crystals,  very  soluble  in  both  alcohol  and  water.     Its  solution 
dissolves  a  large  quantity  of  free  iodine,  acquiring  thus  a 
deep  brown  color. 

500.  Fluorid  of  Potassium  is  obtained  by  the  action  of 
hydrofluoric  acid  on  potash.     It  is  perfectly  analogous  to  the 
preceding  salts,  crystallizes  in  cubes,  and  is  very  soluble  in 
water. 

501.  Sulphuret  of  Potassium. — Sulphur  combines   with 
potassium  in  several  proportions — probably  in  seven.     The 
protosulphuret  of  potassium  is  made  by  melting  together  its 
constituents,  or   better  by  passing  hydrogen  gas  over  the 
neutral  sulphate  of  potash    heated  to   redness.      Water   is 
formed,  and  sulphuret  of  potassium  remains.     It  is  a  bright 
red  solid,  and  forms  a  colorless  solution  in  water,  which  has 

498.  Describe  the  formation  of  bromid  of  potassium.  499.  What 
use  is  made  of  iodid  of  potassium  ?  What  are  its  properties  ?  500. 
Fluorid  of- potassium  is  how  prepared  ?  What  crystalline  form  is 
common  to  all  the  foregoing  salts  ?  501.  What  are  the  compounds 
of  sulphur  and  potassium  ?  Describe  the  sulphurets. 


COMPOUNDS   OF    POTASSIUM.  287 

an  alkaline  reaction.  This  is  a  sulphur  base  of  considerable 
power,  and  combines  with  sulphur  acids  without  decompo- 
sition. Other  acids  decompose  it  with  the  escape  of  sulphu- 
reted  hydrogen.  The  tritosulphuret  of  potassium  (KS3) 
corresponds  to  the  teroxyd  of  the  same  base. 

502.  The  Pentasulphuret  of  Potassium  (persulphuret  KS5) 
is  formed  when  sulphur  is  fused  with  carbonate  of  potash  at  as 
low  a  heat  as  possible  ;  hyposulphite  of  potash  is  formed  at 
the  same  time.     The  persulphuret  is  a  deep  orange-yellow 
solid,  soluble  in  alcohol. 

The  protosulphuret  is  converted  into  the  persulphuret  by 
boiling  in  water  with  four  equivalents  of  sulphur. 

The  Seleniurets  of  Potassium  are  supposed  to  be  like  the 
sulphurets,  but  are  not  much  known. 

503.  Nitrogen  forms  a  compound  with  potassium,  (K3N.) 
When  potassium  is  heated   in  dry  ammonia,  an  olive-green 
solid  is  formed,  which   has  the  composition  expressed  by 
K,NH2.      When   this  is  heated,  ammonia  escapes,  and  a 
gray  body  resembling  graphite  is  left  behind,  which  is  the 
compound  in  question.     Phosphorus  also  forms  a  solid  com- 
pound with  potassium — the  phosphuret  of  potassium — which 
is  decomposed  by  water  with  the  escape  of  spontaneously 
inflammable  phosphureted  hydrogen. 

Unimportant  compounds  are  also  formed  by  potassium 
with  carbon  and  hydrogen ;  but  no  compound  is  known  be- 
tween it  and  silicon  and  boron. 

2.  Salts  of  Potash. 

504.  The  salts  of  potash  are  numerous  and  important. 
We  shall   however  mention  now  only   the  carbonates,  sul- 
phates, nitrata,  and   chlorate.     As  it  will  be  altogether  im- 
possible to  give  even  the  names  of  all  the  salts  of  the  metals, 
we   must   content   ourselves  with   a   selection   of  the   most 
important  and  interesting. 

505.  Carbonate    of   Potash,    KO,CO2  +  2O,  (79-19.) — 
This  salt,  in  an  impure  form,  is  made  on  a  great  scale  in 


502.  The  pentasulphuret  is  what,  and  how  formed  ?  503.  What 
is  the  compound  of  nitrogen  and  potassium,  and  how  formed  ?  What 
other  compounds  of  potassium  with  non-metallic  elements  are 
named  ?  504.  What  is  said  of  the  salts  of  potash,  and  which  will 
be  now  considered  ?  505.  What  is  the  formula  and  atomic  number 
of  the  carbonate  of  potash  ? 


•METALLIC    ELEMENTS. 

this  country,  under  the  name  of  pearlash  and  potash,  which 
is  the  alkali  obtained  from  the  ashes  of  forest  trees,  by  lixi- 
viation  and  combustion. 

The  crude  article  of  commerce  is  contaminated  by  silica, 
sulphate  of  potash,  and  chlorids  of  potassium  and  sodium. 
The  latter  impurity  is  frequently  added  in  the  process  of 
manufacture,  either  through  ignorance,  or  from  fraudulent 
motives.  The  best  potash  is  made  by  using  hot  water  to 
lixiviate  the  ashes,  in  small  leach-tubs.  The  brown  mass 
left  by  evaporating  the  lixivium  to  dry  ness  in  iron  kettles, 
is  the  potash  of  commerce.  This  is  moderately  calcined  to 
burn  off  the  coloring  matter,  when  a  spongy  mass  of  a  fine 
light  blue  color  is  left,  which  is  the  pearlash. 

506.  The  pure  carbonate  is  best    obtained    by  calcining 
the  cream  of  tartar,  (acid  tartrate  of  potash,)  and  dissolving 
out    the    carbonate   from   the  coaly  mass    by  water.      The 
filtered    solution    is    evaporated  to  dryness  in  a  silver  cap- 
sule, and  the  salt  obtained  pure. 

The  carbonate  of  potash  has  a  strong  alkaline  taste, 
turns  cabbage  or  dahlia  paper  green,  and  is  somewhat 
caustic ;  it  dissolves  in  about  twice  its  weight  of  water, 
forming  a  solution,  which  is  much  used  in  the  laboratory. 
It  crystallizes  with  difficulty,  and  takes  up  two  equivalents  of 
water  in  so  doing.  It  is  quite  insoluble  in  alcohol.  This  is 
a  very  deliquescent  salt,  and  must  be  kept  in  well-stopped 
bottles. 

Even  when  most  pure  it  is  apt  to  contain  a  trace  of  silica, 
from  which  it  can  be  freed  by  igniting  the  bicarbonate,  and 
evaporating  its  solution  to  dryness. 

Several  samples  of  American  potash  examined  by  Dr.  L. 
C.  Beck  yielded  73-0;  74-6  ;  75  and  76-9  per  cent,  of  car- 
bonate and  hydrate  of  potash ;  from  6  to  15*per  cent,  of 
chlorids  of  potassium  and  sodium ;  with  from  1  to  15  per 
cent,  of  insoluble  matter.* 

507.  Bicarbonate    of    Potash,   (KO,    CO2  +  HO  CO2,) 


What  crude  forms  of  it  do  we  know?  How  is  the  crude  article 
prepared  ?  How  does  pearlash  differ  from  potash  ?  506.  How  is 
the  pure  carbonate  obtained  ?  What  are  its  properties  ?  What  did 
the  samples  of  American  potash  examined  by  Dr.  Beck  yield  ? 
507.  What  is  the  bicarbonate  of  potash? 

*  Beck's  Manual  of  Chemistry,  p.  228,  2d  edition. 


SALTS   OF    POTASH.  289 

Equiv.  100*19. — This  salt  is  formed  by  passing  a  stream  of 
carbonic  acid  gas  through  a  cold  solution  of  carbonate  of  pot- 
ash. It  crystallizes  in  large  and  beautiful  crystals  referable 
to  the  right  rhombic  system.  Four  parts  of  water  dissolve 
it ;  the  solution  has  an  alkaline  taste  and  reaction,  but  is  not 
caustic ;  by  heat  it  is  converted  to  the  simple  carbonate,  and 
it  loses  a  portion  of  carbonic  acid  by  solution  in  hot  water. 

508.  Sulphate  of  Potash,  KO  SO3,  Equiv.  87-28.— This 
salt  is  usually  prepared  by  neutralizing  the  residue  of  the  nitric 
process,  (312,)  and  is  also  procured  by  saturating  a  concen- 
trated solution  of  potash  by  strong  sulphuric  acid,  added  drop 
by  drop.     It  is  an  anhydrous,  well  crystallized  salt,  which 
decrepitates  with  heat,  and  has  a  density  of  2-4.     It  requires 
100  parts  of  water  to  dissolve  8' 36  parts  of  this  salt  at  32°, 
and  0*096  parts  more  of  the  salt  dissolve  for  every  degree 
above  that. 

509.  Bisulphate  of  Potash,  or  Hydrate  of  Bisulphate, 
(sulphate  of  water  and  potash,)  KO,  S03+HO,  SO3,  Equiv. 
136*37. — This  salt  is  obtained  by  decomposing  nitrate  ofpo- 
tassa  by  two  equivalents  of  oil   of  vitriol,  in  the  process  for 
nitric  acid.     It  cools  into  a  white  crystalline  mass  at  386°*6, 
which  is  very  soluble  in  water,  with  partial  decomposition. 
It  is  dimorphous  in  crystalline  form,  one  of  its  figures  being 
identical  with  crystallized  sulphur.     The  solution  is  strongly 
acid,  and  acts  on  bases  nearly  as  powerfully  as  if  potash 
were  not  present. 

510.  Sesquisulphate  of  Potash,  2KO,  SO3-f  HO,  SO3. — 
This  salt  is  obtained  from  the  nitric  acid  residue,  in  long  silky 
needles,  which  resemble  asbestus.     They  cover  the  previous 
salt  after  long  standing,  with  a  beautiful  vegetation  or  efflo- 
rescence. 

511.  Nitrate  of  Potassa  ,•  Saltpetre;  Nitre;  KO,  NO5, 
Equiv.  101*25. — This  important  salt  is  a  natural  product  in 
the  hot  and  dry  regions  of  India  and  South  America,  being 
formed  by  the   gradual  decomposition  of  animal  matters  in 
the  soil.     It  is  also  formed  artificially  by  heaping  together 
beds  of  old  mortar,  earth,  dung,  and  other  animal  matters, 


Give  its  formula.  What  are  its  properties  ?  508.  What  formula 
has  sulphate  of  potash  ?  How  is  it  prepared  ?  509.  Give  the  for- 
mula of  bisulphate  of  potash  and  its  properties.  510.  What  is  ses- 
quisulphate  of  potash  ?  511.  Where  is  the  nitrate  of  potash  found  ? 
How  is  it  formed  artificially  ? 
25 


290  METALLIC    ELEMENTS. 

and  occasionally  wetting  the  mass  with  fermenting  urine. 
In  some  of  the  caverns  in  Kentucky,  the  soil  on  the  floors 
becomes  strongly  impregnated  with  nitrate  of  lime,  which  is 
decomposed  by  wood  ashes,  and  yields  nitrate  of  potassa. 
In  all  these  cases,  the  nitre  is  obtained  by  lixiviating  the 
nitrous  earth  with  water,  evaporating  and  crystallizing  the 
solution,  redissolving  and  crystallizing  a  second  time,  until 
the  salt  is  obtained  pure. 

512.  Properties.  —  Nitre   crystallizes   in  long,    six-sided 
prisms,  with  dihedral  summits,  derived  from  the  right  rhom- 
bic prism  ;  is  anhydrous,  and  fusible  at  a  heat  under  redness. 
It   is   unaltered  in  the  air,  and  insoluble  in  alcohol,  but  dis- 
solves in  about  3  parts  of  water  at   60°.     In  hot  water  it  is 
much  more  soluble,  100  parts  of  water  at  2060<6,  dissolving 
236  parts  of  the  salt.     Its  solution   has  a  cooling  taste,  and 
antiseptic  properties. 

513.  The  great  quantity  of  oxygen  contained  in  nitre,  and 
the  ease  with  which  it    parts  with  it,  render  it  a  valuable 
agent.     It  is  the  chief  constituent  of  gunpowder,  imparting 
oxygen  to  the  carbon  and  sulphur  in  that  compound,  to  form 
with  explosive  energy  those  gases  which  are  generated  by  the 
combustion  of  the   materials.     It  is  also  much  used  in  all 
pyrotechnic   mixtures,  as  well  as  to  deflagrate  and  scorify 
metals.      The  surface  of  silver  ware   is  often  scorified   by 
nitre,  which  burns  out  the  alloyed  copper,  and  leaves  a  sur- 
face  of  pure    silver.     Good    gunpowder  is  composed  very 
nearly  of  1   equivalent  of  nitre,  3  of  carbon,  and  1  of  sul- 
phur.    Thus  : 

Theoretical  mixture.  English.  Prussian. 
Sulphur,                 11-9                        12-5  11-5 

Charcoal,  13-5  12-5  13-5 

Nitre,  74-6  75-  75- 

Much  of  the  explosive  energy  of  gunpowder  depends  jn 
its  granulation ;  a  fine  dust  of  the  same  composition  with 
powerful  powder,  burns  with  a  rapid  deflagration,  but  with- 
out explosion.  The  gases  formed  from  its  combustion  are 
carbonic  acid  and  nitrogen,  while  sulphuret  of  potassium 

How  is  it  procured  from  the  nitrate  of  lime  ?  512.  What  are  the 
properties  of  nitre  ?  513.  What  renders  nitre  a  valuable  reagent  ? 
Of  what  is  it  the  chief  constituent  ?  What  is  the  constitution  of 
gunpowder  ?  On  what  does  its  explosive  energy  depend  ?  What 
are  the  products  of  its  combustion  ? 


SALTS    OF    POTASH.  291 

remains  as  a  solid  residue.  The  combustion  of  a  squib,  or 
moist  gunpowder,  gives  a  much  more  complicated  result ; 
nitric  oxyd,  sulphureted  hydrogen,  carbonic  acid,  carbonic 
oxyd,  nitrogen,  and  other  products  being  formed.  The  con- 
stitution of  gunpowder  is  varied  according  to  the  use  for 
which  it  is  intended.  Thus,  20  sulphur,  15  charcoal,  and 
65  nitre,  are  used  for  blasting-powder,  and  its  combustion  is 
rendered  still  slower  by  mixing  it  with  several  times  its  bulk 
of  saw-dust.  The  effect  then  is  more  powerful  in  moving 
large  masses  of  rocks. 

514.  Nitrate  of  potassa  has  been  much  used  in  England 
as  a  manure,  and,  as  already  mentioned,  (312,)  is  the  source 
of  the  best  nitric  acid.     It  is  also  employed  (254)  to  yield 
oxygen  gas. 

515.  Chlorate  of  Potash,  KO,  C1O5,  Equiv.  122.60.— 
This  is  the  salt  already  named  (253)  as  the  best  source  of 
pure  oxygen  gas,  of  which  it  yields  a  great  quantity  by  heat. 
It  is  formed  by  passing  chlorine  gas  through  a  strong  solu- 
tion of  carbonate  of  potash,  chlorate  of  potash  and  chlorid 
of  potassium   being   formed,  the  chlorate  being  easily  crys- 
tallized out  by  its  less  solubility  than  the  chlorid  of  potassium. 
The  reaction  is  between  6KO  +  CI=5KC1  +  KO,  Ci05. 

516.  Properties. — Chlorate  of  potash  crystallizes  in  flat 
tables    referable    to   the  oblique  rhombic  prism,  and  has  a 
pearly  lustre.     In   cold  water  (30°)  it  is  very  little  soluble, 
and  100  parts  of  water  at  60°  dissolve  only  6  parts  of  the 
salt.     Its  taste  is  cooling  and  disagreeable,  resembling  nitre. 
It  fuses  below  redness  ;  oxygen  is  given  off,  and  chlorid  of 
potassium  left  behind. 

517.  With    combustible  bodies  its   action    is    more  ener- 
getic than  that  of  nitre.     With  sulphur  and  charcoal  it  forms 
a   compound   that   explodes    by  friction,  and  was  formerly 
much  used   in    the  manufacture  of  lucifer  matches.     With 
sulphur  alone,  it  detonates   powerfully  when  wrapped  in  a 
paper  and  struck  by  a  hammer.     With  phosphorus  its  reac- 
tion is  extremely  violent ;  a  deafening  explosion  follows  the 
slightest  compression  of  the  ingredients,  and  burning  phos- 
phorus is  projected  in  all  directions. 


If  wet,  what  are  they  ?  How  is  blasting-powder  made  more 
efficient  ?  514.  What  other  uses  of  nitre  ?  515.  What  is  chlorate 
of  potassa,  and  how  formed  ?  516.  What  are  its  properties  ?  517. 
What  is  its  reaction  with  combustibles  ? 


292  METALLIC    ELEMENTS. 

All  attempts  to  form  a  gunpowder  of  chlorate  of  potash 
have  failed,  the  action  of  the  mixture  being  so  violent  as  to 
rend  asunder  the  arms  employed.  A  mixture  of  sugar  and 
chlorate  of  potash  is  instantly  inflamed  by  a  drop  of  sulphu- 
ric acid. 

16.  SODIUM. 
Equivalent,  23-27.   Symbol,  Na.  (Natrium.)   Density,  -972. 

518.  Sodium  was  discovered  by  Davy  soon  after  the  dis- 
cover)" of  potassium,  and  in   the  same  way.     It  is  now  pre- 
pared by  a  process  quite  similar  to  that  already  described  (489) 
ibr  potassium  ;  the  carbonate  of  soda  being  used  in  place  of 
the  carbonate  of  potassa. 

This  metal  forms  more  than  40  parts  in  100  of  common 
salt,  and  is  also  frequent  in  various  combinations  in  the  min- 
eral kingdom.  The  ashes  of  sea-plants  afford,  in  place  of  the 
carbonate  of  potash  of  land-plants,  crude  carbonate  of  soda. 

519.  Sodium  is  a  white  metal,  with  a  silvery  brilliancy, 
and  much  resembles  potassium  in  its  general  properties.     Its 
density  is  -972,  and  it  melts  at  194°.     At  common  tempera- 
tures it  is  much  harder  than  potassium,  but  is  easily  moulded 
in  the  fingers.     It  does  not  inflame  on  cold  water,  but  moves 
about  rapidly  in  a  brilliant  sphere,  until  it  is  all  consumed. 
It  may  be  alloyed  with  potassium  by  simple  pressure,  and  is 
then  inflamed  on  water,  or  alone  on  hot  water,  burning  with 
a  bright   yellow  light,  characteristic  of  sodium.     The  same 
color  is  seen  when  a  piece  of  soda-glass,  or  any  mineral  con- 
taining soda,  is  held  in  the  flame  of  the  blowpipe ;  the  flame 
is  instantly  tinged  yellow.     Exposed  to  the  air,  sodium  soon 
falls  to  a  white  powder  of  oxyd  of  sodium. 

The  compounds  of  sodium  are  so  similar  to  those  of  po- 
tassium, that  we  can  pass  them  with  a  brief  notice. 

520.  The  Oxyd  of  Sodium,  NaO,  Equiv.  No.  31-27,  is 
formed   by  decomposing  the  carbonate,  by  the  same  means 
employed  to  form   the  caustic  potash,  (493.)     It  is  a  strong 
alkali,  and  very  caustic.     All  its  salts  are  soluble,  by  which 
it  is  distinguished  from  potash,  whose  chlorid  forms  a  sparingly 
soluble  compound  with  chlorid  of  platinum. 


Can  gunpowder  be  made  from  it  ?  518.  Who  discovered  sodium, 
and  how  is  it  prepared  ?  519.  What  are  its  properties  ?  520.  What 
is  its  oxyd  ?  How  is  it  distinguished  ? 


SODIUM.  293 

521.  Chlorid  of  Sodium;    Sea   Salt;  Common   Salt; 
NaCl,  58-68. — This   familiar  and  abundant  salt  is  too  well 
known  to  need  much  description.     It  is  formed  when  sodium 
burns  in  chlorine  gas,  as  well  as  when  soda  or  its  carbonate 
is  neutralized  by   hydrochloric  acid.     Common  salt    forms 
about   27  of  every  1000  parts  of  sea-water,  and  in  warm 
climates,  especially  in  the  West  Indies,  sea-water  is  evapo- 
rated in  large  quantities  by  the  sun's  heat,  to  obtain  salt. 
Numerous  saline  springs  are  found  in  New  York,  Ohio,  Ken- 
tucky, and  other  places  in  this  country,  (457,)  which  afford 
vast  quantities  of  salt  by  evaporation.     The  brine  springs  in 
Onondaga  county,  N.  Y.,  are  among  the  most  valuable,  and 
have  been  worked  since    1789.     This  water   contains  one 
seventh  part  of  dry  salt. 

522.  Common  salt  crystallizes  in  cubes,  which  are  anhy- 
drous, and  crackle  or  decrepitate  when  heated.     It  requires 
2-7  parts  of  water  for  its  solution,  and  is  equally  soluble  in 
hot  and  cold  water.     Its   density  is  2-557,  and  in  pure  alco- 
hol it  is  scarcely  at  all  soluble.     It  fuses   at  redness,  and 
sublimes  in  vapor  at  a  higher  temperature.     It  is  employed 
for  this  reason  to  glaze  earthen  ware,  since  its  vapor  is  de- 
composed by  the  oxyd  of  iron  of  the  clay,  chlorid  of  iron 
being  driven  off,  while  soda  unites  with  the  silica  of  the  clay 
to  form  the  glaze. 

The  Bromid  and  lodid  of  sodium  resemble  the  correspond- 
ing compounds  of  potassium,  and  like  them  crystallize  in 
cubes. 

523.  Carbonate  of  Soda  is  manufactured  on  a  very  great 
scale  from  common  salt,  (421,)  and   is  found  nearly  pure  in 
the  arts.     It  crystallizes  in  oblique  rhombic  prisms,  with  ten 
atoms   of    water    of   crystallization,    (NaO,CO2  +  10HO.) 
This  salt  is  sometimes  found  native.     The  common  form  of 
carbonate  of  soda  is  a  dry  powder,  called  soda  ash,  which  is 
an  impure  mixture  of  chlorid,  sulphate,  &c.     The  pure  salt 
has  58-58   per  cent,  of  soda,  and  41-42   of  carbonic  acid. 
Carbonate  of  soda  dissolves  in  about  five  parts  of  water,  and 
the  solution  has  a  disagreeable  alkaline  taste. 

524.  Bicarbonate  of  Soda,  HO,CO2-f  NaO,CO2,  Equiv. 

521.  Describe  common  salt.  How  is  it  procured  ?  How  murh 
does  sea- water  contain  ?  522.  Give  the  properties  of  salt.  How 
does  it  act  as  a  glaze  ?  523.  From  what  is  carbonate  of  soda  chiefly 
made  ?  What  are  its  properties  and  constitution  ?  524.  How  does 
the  bicarbonate  differ  from  the  carbonate  of  soda  ? 
25* 


294-  METALLIC    ELEMENTS. 

84-27. — Tliis  salt  is  formed  when  carbonic  acid  is  passed 
through  a  saturated  solution  of  the  neutral  carbonate.  It  is 
deposited  in  a  dry  white  powder,  which  requires  13  times  its 
weight  of  cold  water  to  dissolve  it.  Its  taste  is  alkaline,  but 
much  less  disagreeable  than  the  pure  carbonate.  It  is  much 
used  in  medicine  and  in  domestic  economy. 

This  salt  is  thrown  down  as  a  granular  precipitate,  when 
bicarbonate  of  ammonia  is  added  in  fine  powder  to  a  solution 
of  an  equal  weight  of  common  salt. 

The  sesquicarbonate  of  soda,  (trona,)  (2NaO-f-3CO2-f 
4HO,)  occurs  in  nature,  being  found  in  Africa  and  South 
America.  It  is  little  soluble,  and  unalterable  in  the  air,  and 
crystallizes  in  right  rhomboidal  prisms. 

525.  Sulphate  of  Soda,  Glauber's  Salt,  NaOSO3+10HO, 
Equiv.  71-36  +  90.— This  salt  is  the  result  of  the  hydrochlo- 
ric acid   process,  (418,)  and   is  also  found   native,  and   in 
solution  in  natural  waters.     It    fuses   by    heat    in   its   own 
water  of  crystallization,  and  loses   its  water  (effloresces)   in 
dry  air,  and  falls  into  a  white  powder.     Water  dissolves  half 
its  own  weight  of  sulphate  of  soda  at  91°,  but  only  42.65 
parts  at  the  boiling  temperature. 

A  saturated  solution  may  be  cooled  under  a  film  of  oil,  or 
in  a  vessel  corked  tight  while  hot,  and  when  it  is  cold  no 
crystals  will  be  deposited  until  the  air  strikes  the  surface,  or 
a  small  crystal  is  dropped  into  the  solution,  when  the  whole 
mass  instantly  becomes  solid.  This  salt  is  much  used  in 
medicine  as  an  aperient. 

526.  The  great  use  of  sulphate  of  soda  is  in  forming  soda 

ash,  or  crude  carbonate  of  soda, 
for  the  use  of  glass-makers  and 
soap-boilers.  For  this  purpose 
the  sulphate  is  strongly  heated  in 
a  reverberatory  furnace,  mixed 
with  charcoal  or  coke,  and  car- 
bonate of  lime.  The  sulphate  is 
decomposed,  sulphuret  of  calcium  and  carbonate  of  soda 
being  formed  ;  the  latter  is  dissolved  out  by  hot  water,  and 
purified  by  crystallization. 


What  are  its  properties  ?  What  is  the  sesquicarbonate  ?  525. 
Give  the  composition  of  sulphate  of  soda.  What  of  its  solubility? 
How  does  its  saturated  solution  act  if  cooled  away  from  contact  with 
the  air  ?  526.  What  is  the  chief  use  of  sulphate  of  soda  ? 


COMPOUNDS    OP    SODIUM.  295 

527.  Nitrate  of  Soda,  Soda  Saltpetre,  NaO,NO6.— This 
salt  is  found  in  India  and  South  America,  where  extensive 
plains  are  covered  by  it,  as  at  Tarapaca  in  Chili,  and  Iquique. 
It  resembles  nitrate  of  potassa,  but  cannot  be  used  to  replace 
that  salt  in  gunpowder,  on  account  of  its  strong  disposition  to 
attract  water  from  the  air  and  grow  damp.     It  is  generally 
employed  however  in  making  nitric  acid,  and  also  as  a  fertil- 
izer in  agriculture. 

This  is  a  white  salt,  crystallizing  in  rhombs,  specific  grav- 
ity 2-09,  very  soluble,  with  a  cooling  taste,  and  deflagrates 
on  burning  coals  with  a  strong  yellow  light. 

528.  The  phosphates  of  soda  are  a  very  interesting  and 
important  class  of  salts,  the  study  of  which   has  done  much 
to   advance   our  knowledge  of  theoretical  chemistry.     We 
will  mention  five  phosphates  of  soda,  three  tribasic,  one  bi- 
basic,  and  one  monobasic  phosphate. 

Phosphate  of  Soda. — Common  Tribasic  Phosphate,2N&O 
HO,PO5  +  24HO. — This  beautiful  salt  is  prepared  by  pre- 
cipitating the  acid  phosphate  of  lime,  (317,)  with  a  slight 
excess  of  carbonate  of  soda.  It  crystallizes  in  oblique 
rhombic  prisms,  which  are  efflorescent.  The  crystals  dissolve 
in  four  parts  of  cold  water,  and  undergo  the  aqueous  fusion 
when  heated.  The  salt  has  a  pleasant  saline  taste,  and  is 
purgative  ;  its  solution  is  alkaline  to  test-paper. 

A  second  tribasic  phosphate,  sometimes  called  subphos- 
phate,  3NaO,  P05  +  24HO,  is  obtained  by  adding  solution  of 
caustic  soda  to  the  preceding  salt.  The  crystals  are  slender 
six-sided  prisms,  soluble  in  5  parts  of  cold  water.  It  is  de- 
composed by  acids,  even  the  carbonic,  but  suffers  no  change 
by  heat,  except  the  loss  of  its  water  of  crystallization.  Its 
solution  is  strongly  alkaline. 

A  third  tribasic  phosphate,  often  called  superphosphate 
or  biphosphate,  NaO,2HO,PO5  +  2HO,  may  be  obtained  by 
adding  phosphoric  acid  to  the  ordinary  phosphate,  until 
it  ceases  to  precipitate  chlorid  of  barium,  and  exposing  the 
concentrated  solution  to  cold.  The  crystals  are  prismatic, 
very  soluble,  and  have  an  acid  reaction.  When  strongly 


527.  What  is  said  of  nitrate  of  soda  ?  What  is  its  constitution  and 
use?  528.  What  is  said  of  the  phosphates  of  soda,  and  how  many 
are  named  ?  Give  the  composition  and  properties  of  common  phos- 
phate of  soda.  What  is  the  composition  of  the  subphosphate  ?  What 
that  of  the  third  tribasic  phosphate  ? 


296  METALLIC    ELEMENTS. 

heated,  the  salt  becomes  changed  into  monobasic  phosphate 
of  soda. 

529.  Microcoxmic  Salt,  or  Phosphate  of  Soda  and  Am- 
monia, (HO,NH4O,NaO,PO5  +  8HO,)  is  much  used  in  blow- 
pipe  operations  as  a  flux.     It  is  formed  by  dissolving  with  a 
gentle  heat,  1  part  of  chlorid  of  ammonium  and  6  or?  parts 
of  phosphate  of  soda,  in  2   of  water.     Chlorid   of  sodium  is 
formed,  and  the  microcosmic  salt  crystallizes  out  in  rhombic 
prisms,  which  lose  8HO  by  heat. 

530.  Bibasic  Phosphate  of  Soda,  Pyrophosphate  of  Soda, 
2NaO,  PO5-f  10HO. — Prepared  by  strongly  heating  common 
phosphate   of  soda,  dissolving  the  residue  in  water,  and  re- 
crystallizing.     The  crystals  are  very  brilliant,  permanent  in 
the  air,  and  less  soluble  than  the  original  phosphate ;  their 
solution  is  alkaline.     A  bibasic  phospnate,  containing  an  equiv- 
alent of  basic  water,  has  been  obtained  ;  it  does  not,  however, 
crystallize. 

531.  Monobasic  Phosphate  of  Soda,  Metaphosphate  of 
Soda,  NaO,  P05. — Obtained  by  heating  either  the  acid  tri- 
basic  phosphate,  or  microcosmic  salt.     It  is  a  transparent, 
glassy  substance,  fusible  at  a  dull  red-heat,  deliquescent,  and 
very  soluble  in  water.     It  refuses  to  crystallize,  and  dries  up 
in  a  gum-like  mass. 

The  tribasic  phosphates  give  a  bright  yellow  precipitate 
with  a  solution  ofnitrate  of  silver;  the  bibasic  and  monobasic 
phosphates  afford  white  precipitates  with  the  same  substances. 
The  salts  of  the  two  latter  classes,  fused  with  excess  of  car- 
bonate of  soda,  yield  the  tribasic  modification  of  the  acid. 

532.  Borax;  Biborate  of  Soda  ;  NaO,  2BO3-f  10HO.— 
Borax  crystallizes  in  right  rhomboidal  prisms,  which  are  solu- 
ble in  15  or  16  parts  of  water;  the  solution  has  an  alkaline 
reaction  and  sweetish  alkaline  taste.     It  loses  its  water  by 
heat,  and  being  very  fusible,  is  much   used   in  metal lurgic 
processes  and  as  a  blowpipe  reacjent.     It  is  entirely  procured 
from   natural  sources   of  boracic   acid    ajready  mentioned, 
(367,)  and  from  the  waters  of  several  lakes  in  Thibet  which 
contain  it. 


When  heated,  this  salt  becomes  what  ?  529.  What  is  the  micro- 
cosmic  salt  ?  How  is  it  formed  ?  530.  How  is  bibasic  phosphate 
formed  ?  What  is  its  formula  ?  531.  What  is  the  composition  of 
the  monobasic  phosphate  of  soda  ?  What  are  the  reactions  of  the 
phosphates  of  soda  with  tests  ?  532.  Give  the  composition  of  borax. 
What  is  its  use  ? 


297 


Manufacture  of  Glass. 


533.  Silicates  of  Soda.  —  Both    soda  and  potash  form 
compounds    with   silicic   acid    (361)    by  fusion,  which    are 
silicates,   but  of  uncertain  composition.     If  4  parts  of  the 
alkali  are  used  to  1   of  the  silica,  the  glass  is  soluble,  but 
whatever  may  be  the  proportions  used,  the  resulting  silicate 
is  always  an  uncrystalline,  homogeneous,  transparent  mass. 
The  "  soluble  glass"  formed   by  fusing  together  8  parts  of 
carbonate  of  soda  (or  10   of  carbonate  of  potash)  with   15 
parts  of  pure  sand  and   1   of  charcoal,  is  insoluble  in  cold, 
but  dissolves  in  4  or  5  parts  of  hot  water,  forming  a  sort  of 
varnish,  which    may  be  applied   to  wood   or  manufactured 
stuffs,  which  are  to  a  good  degree  protected  by  it  from  the 
action  of  fire. 

534.  Glass  is  a  variable  compound  of  the  silicates  of  pot- 
ash, soda,  lime,  and  alumina,  with  oxyds  of  lead  and  iron, 
fused  together  by  a  very  high   and   long-continued   heat,  in 
proportions  sujted  to  the  object  for  which  the  glass  is  to  be 
used.     This  is  not  the  place  to  describe  the  varied  and  inter- 
esting manipulations  by  which  the  fused  material  is  blown, 
cast,  moulded,  or  pressed  into  the  countless  forms  of  utility 
and  ornament,  which  the  wants  of  society  demand.     A  visit 
to  a  large  glass-house  is  always  full  of  instruction  and  plea- 
sure. 

535.  Window-glass  is  a  silicate  of  soda  and  lime,  which 
requires  an  intense  heat  for  its  fusion,  and  forms  a  very 
hard  and  brilliant  glass.     Plate  glass,  such  as  is  used  for 
mirrors,  crown  glass  employed  for  glazing,  and  the  beautiful 
Bohemian  glass,  are  all  silicates  of  potash  and  lime. 

Crystal  glass  is  formed  by  fusing  together  120  parts  of 
fine  sand,  40  purified  potash,  36  of  litharge  or  minium,  (oxyd 
of  lead,)  and  12  of  nitre.  This  forms  a  very  fusible  glass, 
easily  worked,  and  so  soft  as  to  be  cut  and  polished,  with 
comparative  ease. 

Green  bottle  glass  is  usually  a  silicate  of  alumina,  with 
oxyds  of  iron  and  magnesia,  and  potash  or  soda.  It  is 
formed  of  the  cheapest  refuse  of  the  soap-boiler's  waste,  and 
lime  which  has  been  used  to  make  caustic  potash  or  soda. 


533.  What  is  said  of  the  silicates  of  soda  ?  What  is  the  soluble 
glass  ?  534.  What  is  glass  ?  535.  What  is  window  and  plate  glass  ? 
What  is  crystal  glass  ?  Bottle  glass  ? 


298  METALLIC    ELEMENTS. 

All  glass  must  be  carefully  annealed  after  it  is  made,  by 
slow  cooling,  or  it  will  break  in  pieces  with  the  least  scratch 
or  jar.  Slow  cooling  of  heated  glass  for  many  hours,  or 
even  days,  for  heavy  articles,  renders  the  mass  homogeneous 
and  less  brittle. 


17.    AMMONIUM. 

Equivalent,  18.06.     Symbol,  NH4,  (hypothetical.) 

536.  Ammonium,  (NH4.) — This  compound  of  hydrogen 
and  nitrogen  has  never  been  isolated,  though  we  have 
reason  to  believe  in  its  existence.  When  a  solution  of  am- 
monia, or  of  sal-ammoniac,  is  electrolized,  nitrogen  escapes 
at  the  H-  side  and  hydrogen  at  the  —  side ;  but  if  the  latter 
pole  is  made  by  using  a  portion  of  mercury,  no  hydrogen  is 
evolved,  but  the  mercury  swells  up,  loses  its  fluidity,  becomes 
like  soft  butter,  and  gradually  attains  many  times  its  original 
bulk,  having  the  lustre  and  general  character  of  an  amalgam. 
A  more  simple  mode  of  forming  this  amalgam,  consists  in 
making  a  little  potassium  or  sodium  combine  by  heat,  with 
about  100  times  its  weight  of  metallic  mercury.  This  alloy, 
when  placed  in  a  strong  solution  of  sal-ammoniac,  begins  at 
once  to  increase  in  volume  by  the  formation  of  the  ammoni- 
acal  amalgam,  until  it  has  attained  very  many  times  its  origi- 
nal bulk,  and  has  a  pasty,  bulyraceous  consistence. 

When  the  alloy  of  potassium  is  placed  in  hydrochloric  acid, 
the  alkaline  metal  decomposes  the  acid,  forming  chlorid  of 
potassium  and  evolving  hydrogen.  If  we  substitute  for  the 
acid  (chlorid  of  hydrogen)  a  solution  of  chlorid  of  zinc, 
ZnCl,  a  like  decomposition  ensues  ;  but  the  zinc,  instead  of 
being  set  free  like  the  hydrogen,  combines  with  mercury  to 
form  an  amalgam.  The  present  reaction  is  precisely  similar ; 
chlorid  of  ammonium,  NH4Cl,  being  substituted  for  the  chlo- 
rid of  zinc  ;  the  ammonium  which  is  liberated,  combines  with 
the  mercury  and  forms  the  light  pasty  amalgam.  It  crystal- 


What  treatment  does  all  glass  require  to  make  it  fit  for  use  ?  536. 
What  is  ammonia  and  how  formed  ?  What  more  simple  mode  of 
forming  the  ammoniacal  amalgam  is  also  described  ?  How  does  the 
alloy  of  mercury  and  potassium  act  in  hydrochloric  acid  ?  How  if 
we  substitute  chlorid  of  zinc  for  the  acid  ?  What  amalgam  is  then 
formed  ?  Explain  this  reaction. 


AMMONIUM.  299 

lizes  in  cubes  at  32°,  whereas  pure  mercury  is  fluid  even  at  a 
temperature  of  — 39°  F.  It  is  evident  that  it  has  combined 
with  something  which  has  given  it  new  properties.  This  is 
supposed  to  be  the  metallic  radical  ammonium.  The  spongy 
mass,  as  soon  as  the  electric  action  ceases,  rapidly  suffers 
decomposition.  Ammonia  and  hydrogen  are  set  free  in  the 
proportion  of  1  to  2,  and  the  mercury  regains  its  original 
state  unaltered.  Berzelius  and  other  able  chemists  explain 
this  reaction,  on  the  ground  that  the  ammonia,  by  gaining  an 
additional  equivalent  of  hydrogen,  assumes  the  peculiar 
character  of  a  metal,  and  unites  with  mercury,  forming  an 
amalgam.  This  hypothetical  metal  can  replace  potassium 
and  sodium  perfectly  in  combination,  and  is  therefore  isomor- 
phous  with  them.  All  the  salts  of  ammonia  are,  on  this 
view,  derived  from  this  radical,  and  its  union  with  the  second 
class  gives  us  a  series  of  bodies  analogous  to  the  chlorids, 
bromids,  &c.,  of  the  other  electro-positive  bases. 

Salts  of  Ammonium. 

537.  Chlorid  of  Ammonium;  Sal  Ammoniac,  NH4C1. — 
This  salt  occurs  in  nature,  sometimes  quite  pure,  as  at  De- 
ception Island,  and  in  volcanic  districts  generally.  It  was 
originally  prepared  in  Egypt,  by  sublimation  from  the  soot 
of  the  burnt  camePs-dung.  It  is  also  obtained  largely  from 
the  ammoniacal  waters  of  the  gas-works.  It  is  purified  by 
evaporating  the  crude  solutions  to  dryness,  after  treating 
them  with  a  slight  excess  of  hydrochloric  acid  to  neutralize 
the  free  ammonia,  and  subliming  the  dry  mass  in  iron  vessels. 

It  has  a  sharp  saline  taste,  corrodes  metals  powerfully,  is 
soluble  in  three  parts  of  cold  water,  and  crystallizes  from  its 
solution  in  octahedrons.  The  sublimed  salt  has  a  fibrous 
texture,  and  is  very  tough  and  difficult  to  pulverize. 

The  formation  of  this  compound  is  easily  shown  by  using 
the  apparatus  already  figured,  (435,)  with  hydrochloric  acid 
in  one  flask  and  strong  ammonia  water  in  the  other ;  the 
commingling  of  the  dry  gases,  driven  over  by  heat  to  the 
central  bottle,  fills  it  with  a  white  cloud  of  sal  amjnoniac, 
C1H  +  NH3=C1NH4. 


What  are  its  properties  ?  What  does  its  decomposition  yield  ? 
In  this  view  how  are  the  ammoniacal  salts  constituted  ?  537.  How 
is  sal  ammoniac  found  in  nature,  and  how  formed  artificially  ?  What 
are  its  properties  ?  How  is  its  formation  illustrated  in  the  class- 
room ?  Give  the  reaction. 


300 


METALLIC    ELEMENTS. 


538.  Sulphuret  of  Ammonium  and  Hydrogen,  (hydro- 
sulphuret   of  ammonia,)   NHtS-fHS. —  This   very  useful 
compound  is  formed  by  passing  a  long-continued,  slow  cur- 
rent of  sulphurated  hydrogen  from  the  gas-bottle  (a)  through 

the  bottles  d,  e,/, 
g,  filled  with 
strong  water  of 
ammonia.  This 
arrangement  is  a 
simple  form  of 
Woulfe's  bottles, 
(442.)  A  single 
bottle  of  ammonia, 
(as  b)  is  sufficient 
for  all  common 
purposes.  It  should  be  kept  cold.  The  ammonia  absorbs  an 
enormous  quantity  of  the  gas,  and  the  resulting  sulphuret, 
which  has  the  strong  odor  of  the  gas,  is  colorless  at  first,  but 
gradually  assumes  a  yellow  color.  It  is  an  invaluable  reagent 
as  a  precipitant  of  the  metals,  and  is  also  used  in  medicine. 

There  are  several   simple  sulphurets  of  ammonium,  but 
they  are  of  no  particular  interest. 

539.  Sulphate    of  Ammonia,  or  Sulphate  of  Oxyd  of 
Ammonium,  NH4O,  SO3-f  HO. — This  salt,  which  is  a  power- 
ful  fertilizer,   is   procured  in  the  large  way  by  neutralizing 
the  ammoniacal  liquor  of  the  gas-works   by  sulphuric  acid  : 
or  it  may  be  easily  obtained  pure  by  neutralizing  dilute  sul- 
phuric acid  with  carbonate  of  ammonia. 

540.  Carbonates  of  Ammonia. — There   are   several   of 
these  salts.     The  common  white  sal-volatile  of  the  shops, 
with  a  pungent  smell  and  alkaline  reaction,  is  nearly  a  ses- 
quicarbonate,  (2NH4O,3CO2.)     Exposed  to  the  air,  this  salt 
becomes  a  white  inodorous  powder,  which   is  a  bicarbonate. 
The  sesquicarbonate  is  a  very  valuable   salt  to  the  chemist, 
and  forms  the  basis  of  the  smelling-bottles  so  much  in  use. 
The  dry  white  powder  formed  by  the  contact  of  dry  carbonic 
acid    and    ammonia  in  an  apparatus  like  that  before  used, 
(435,)  is  a  neutral   anhydrous   carbonate,  (NH3,  CO2,)  very 
pungent,  volatile,  and  dissolving  readily  in  water. 


538.  How  is  sulphuret  of  ammonium  formed  ?  What  is  its  com- 
position ?  What  its  properties  and  uses  ?  539.  What  is  the  composi- 
tion of  sulphate  of  ammonia  ?  540.  What  carbonates  of  ammonia 
Are  named  ?  What  is  the  sal-volatile  ?  What  is  the  inodorous  salt  ? 


BARIUM.  301 

541.  Nitrate  of  Ammonia,  or  Nitrate  of  Oxyd  of  Am- 
monium, (NH4O,  NO5.) — This  salt  has  already  been  noticed 
(305)  under  the  description  of  nitrous  oxyd.     Its  crystals 
resemble  nitre,  deliquesce  in  moist  air,  and  dissolve  in  2  parts 
of  cold  water,  the  solution  sinking  the  thermometer  to  zero, 
(111.)     It  deflagrates  on  burning  coals  like  nitre. 

542.  All  the  ammoniacal  salts  are  volatilized  by  a  high 
temperature,  yield  the  ammoniacal  odor  by  trituration  with 
caustic  potassa  or  lime,  only  boiling  with  solutions  of  potash. 
They  are  all  soluble,  and  give  a  sparingly  soluble,  yellow, 
crystalline  precipitate  with  chlorid  of  platinum. 

18.    LITHIUM. 

Equivalent,  6-43.     Symbol,  L. 

543.  This   very  rare   metal  is   a   constituent   of  several 
minerals,   as    spodumene,   petalite,    lithia-mica,   &c.,    from 
whose  decomposition   by  a  particular  process,   hydrate  of 
lithia  is  obtained,  the  electrolysis  of  which  afforded  Davy  a 
white  oxydizable  metal  analogous   to  sodium.     Its  atomic 
number  is  far  below  that  of  any  other  metal,  and  only  carbon 
and  hydrogen  are  lower  in  the  scale  of  equivalents  ;  this 
gives  its  oxyd  a  very  high  power  of  saturating  acids. 

The  oxyd  (LO)  is  an  alkali,  but  much  less  soluble  than 
potash  and  soda.  Its  sulphate  is  a  beautiful  salt,  and  gives  a 
rosy  flame  to  alcohol.  The  lithia  compounds  all  give  this  tint 
to  the  outer  flame  of  the  blowpipe.  Its  name  is  from  lithos, 
a  stone,  in  allusion  to  the  natural  origin  of  this  alkali. 


CLASS  II.    METALS  OF  THE  ALKALINE  EARTHS. 

19.       BAKIUM. 

Equivalent,  68.55.     Symbol,  Ba. 

544.  Barium  is  a  silver- white  malleable  metal,  which  is 
easily  oxydized,  and   melts  below  a  red  heat.     It  was  pro- 

541.  Describe  the  nitrate  of  ammonia.  How  does  it  affect  the 
thermometer  while  dissolving  ?  542.  How  are  the  ammoniacal 
salts  characterized  ?  543.  What  is  the  equivalent  of  lithium  ?  In 
what  minerals  is  it  found  ?  How  is  its  oxyd  characterized  ?  What 
property  have  all  the  lithia  compounds  ?  544.  What  is  barium  ? 
26 


302  METALLIC    ELEMENTS. 

cured  by  Davy  by  a  process  similar  to  that  which  yielded 
potassium,  &c.  It  is  better  obtained  by  passing  vapor  of 
potassium  over  baryta  (oxyd  of  barium)  healed  to  redness  in 
an  iron  tube.  Mercury  dissolves  out  the  reduced  metal,  and 
the  amalgam  is  then  distilled. 

545.  Baryta,  or  Protoxyd  of  Barium,  BaO. — Baryta  is 
best  obtained  by  decomposing  the  nitrate  at  a  red  heat.     It  is 
a  dry,  gray  powder,  which  combines  with  water  to  form  a 
hydrate,  slaking  with  the  evolution  of  great  heat  and  even 
light.     The  hydrate   dissolves   in  two  parts  of  hot  water,  or 
twenty  of  cold,  and  crystallizes  in  flat  tables.     The  aqueous 
solution  is  a  valuable  reagent. 

Sulphate  of  baryta,  or  heavy  spar,  is  found  abundantly  as 
an  associate  of  other  minerals  in  veins ;  and  from  it,  or  the 
native  carbonate  of  baryta,  all  the  artificial  compounds  of 
barium  arc  formed. 

546.  The  Peroxyd  of  Barium,  BaO2,  is  formed  by  pass- 
ing pure  oxygen   gas  over  the  oxyd   heated  to  redness  in  a 
porcelain  tube.     It  is  chiefly  interesting  as  being  the  means 
of  procuring  the  peroxyd  of  hydrogen,  (410.) 

Chlorid  of  Barium,  BaCl  +  2HO.— This  salt  occurs  in 
white  tabular  crystals,  containing  two  equivalents  of  water 
which  are  expelled  by  heat.  It  dissolves  in  a  little  more  than 
twice  its  weight  of  cold  water,  and  the  solution  is  a  valuable 
reagent  for  detecting  the  presence  of  sulphuric  acid. 

547.  The  Nitrate  of  Baryta,  (BaO,  NO5O)  is  also  a  solu- 
ble white  salt,  which  crystallizes  in  anhydrous  octahedrons, 
and  dissolves  in  eight  parts  of  cold  or  three  parts  of  hot  water. 
Both  it  and  the  chlorid  are  prepared  by  dissolving  the  native 
or  artificial  carbonate  in  the  proper  acid. 

Sulphate  of  Baryta — Heavy  Spar,  (BaO,  SO3,)  is  a  mine- 
ral found  abundantly  in  many  places  in  this  country,  as  at 
Cheshire,  Ct.  It  crystallizes  in  tabular  modifications  of  the 
rhombic  prism,  often  very  beautiful.  It  is  also  found  mas- 
sive at  Pillar  Point  in  N.  Y.  Its  high  specific  gravity  (4*3 
to  4-7)  gives  it  the  name  of  heavy  spar.  It  is  quite  insoluble 
in  water  or  acids,  and  not  easily  decomposed.  When  strongly 

How  obtained  ?  545.  From  what  substances  are  the  barium  salts 
formed?  Characterize  baryta  and  its  action  with  water.  546.  How 
is  peroxyd  of  barium  formed,  and  for  what  used  ?  Give  the  charac- 
ters of  the  chlorid  of  barium.  For  what  is  it  a  test  ?  547.  How  is 
the  nitrate  of  baryta  characterized  ?  How  is  heavy  spar  found  in 
nature  ? 


STRONTIUM.  303 

heated  with  charcoal  powder,  however,  it  suffers  decompo- 
sition, (BaO,  SO3-f  4C  =  BaS-f  4CO);  carbonic  oxyd  is 
given  off,  and  the  soluble  sulphuret  of  barium  may  be  dis- 
solved out  from  the  coaly  mass. 

Sulphate  of  baryta  is  extensively  ground  up  as  a  pigmenl, 
being  mixed  with  white  lead  as  an  adulteration. 

548.  Carbonate  of  Baryta,  BaO,  CO2,  or  the  witherite  of 
mineralogists,  is  a  mineral  of  some  interest,  and  useful  as  the 
chief  source  of  the  various  compounds  of  baryta.     All  the 
soluble  baryta  salts  are   poisonous,  and  their  presence  may 
always  be  detected  by  sulphuric  acid,  with  which  they  form 
an  insoluble  sulphate. 

20.    STRONTIUM. 

Equivalent,  43-78.     Symbol,  Sr. 

549.  Strontium   is   obtained   from  its  oxyd  in  the  same 
manner   as  barium,  and  like  it  is  a  white  metal,  oxydized 
easily  in  air,  and  decomposing  water  at  common   tempera- 
tures.    There  are  two  oxyds,  the  protoxyd  and  the  peroxyd 
of  strontium,  similar  in  properties  to  the  like  oxyds  of  barium. 
The  sulphate  of  strontia,  (celestine,)  is  a  rather  abundant 
mineral,  and  the  carbonate  (strontianite)  is  much  esteemed 
by  mineralogists.     They  are  very  similar   in  properties  to 
the  sulphate  and  carbonate  of  baryta. 

550.  The  Chlorid  of  Strontium  (SrCl-f  9HO)  is  a  deli- 
quescent salt,  soluble  in  two  parts  of  cold  water.     It  loses  its 
water  of  crystallization  by  heat.     Both  it  and  the  nitrate  of 
strontia  (SrO,  NO5,)  are  much  employed  by  pyrotechnists  in 
forming  the  red  jire  of  theatres  and  fire-works.     All  the 
compounds  of  strontium  give  a  peculiar  red  tint  to  the  flame 
of  the  blowpipe,  while  the  barytic  salts  do  not.     The  salts  of 
strontia  are  not  poisonous. 

21.    CALCIUM. 

Equivalent,  20.     Symbol,  Ca. 

551.  Calcium  is  a  yellowish  white  metal,  obtained  like 

Give  its  formula  and  properties.  548.  What  is  carbonate  of 
baryta  ?  What  character  have  the  soluble  salts  of  baryta  ?  How  is 
their  presence  detected  ?  549.  How  is  strontium  obtained  and  how 
characterized  ?  What  familiar  salts  of  this  metal  are  found  native  ? 
550.  Describe  the  chlorid  of  strontium.  What  is  it  used  for  ?  551. 
What  is  calcium  and  how  is  it  obtained  ? 


304  METALLIC    ELEMENTS. 

barium,  and  has  so  strong  a  disposition  to  combine  with  oxy- 
gen that  it  is  difficult  to  observe  its  properties. 

552.  Protoxyd   of  Calcium — Lime,  CaO.  —  This  most 
valuable  substance,  so  well  known  as  quick  lime,  is  procured 
in  a  state  of  great  purity,  by  heating  the  stalactites   from 
Scoharie  Cave,  N.  Y.,  or  Weir's  Cave,  Va.,  in  a  close  cruci- 
ble for  some  hours.     The  carbonic  acid  and  organic  coloring 
matters   are   driven   off,  and  pure  white   oxyd   of  calcium 
remains.     This  is  an  infusible,  rather  hard   body,  having  a 
great  affinity  for  carbonic  acid  and   for  water,  with  which  it 
combines  to  form  a  hydrate,  evolving  great  heat.     The  pre- 
paration of  common  mortar  used   in  building  illustrates  this 
property  on  a  large  scale.     The  dry  hydrate  is  a  bulky  pow- 
der, having  one  equivalent  of  water,  which  may  be  again  ex- 
pelled fjy  heat.     It  is  soluble  in  about  500  parts  of  cold,  and 
less  so   in   hot  water.     The  solution  (lime  water)  is  a  very 
valuable  reagent  to  the  chemist,  and  is  also  used  as  an  anta- 
cid  in   medicine.     Exposure  to  air  decomposes  it,  forming 
the  carbonate  of  lime.     The  solution  has  a  strong,  disagree- 
able alkaline  taste,  and  changes  vegetable  colors. 

Common  lime  is  prepared  by  heating  limestone  (carbon- 
ate of  lime,)  in  large  stone  furnaces,  filled  from  the  top  with 
the  limestone  and  fuel ;  the  fire  is  kept  up  constantly,  by 
renewed  charges  of  the  materials  at  top,  while  the  prepared 
caustic  lime  is  drawn  out  at  the  bottom. 

553.  Mortar  acts  as  a  cement  by  the  slow  formation  of  a 
carbonate  of  lime,  which  binds  together  the  grains  of  sand 
that  make  up  the  greater  part  of  the  mortar.     The  smaller 
the  portion  of  lime  used,  the  more  firm  will  be  the  cement  at 
last ;  but  it  is  then  so  much  more  difficult  to  work,  that  an 
excess  of  lime  is  usually  employed.     The  presence  of  oxyd 
of  iron   and   manganese,  of  alumina,  magnesia,  silica,  and 
other  like  substances,  in  a  limestone  gives  the  lime  prepared 
from  it  the  property  of  hardening  under  water,  which  is  hence 
called  hydraulic  lime. 

Lime  is  much  used  in  improved  agriculture,  as  a  manure. 
It  acts  to  decompose  vegetable  matters,  to  neutralize  acids, 
dissolve  silica,  and  retain  carbonic  acid.  It  is  always  present 

What  is  its  oxyd  ?  552.  How  is  quick  lime  prepared  ?  Give  its 
properties.  How  does  it  act  with  water  ?  How  much  water  dis- 
solves it  ?  What  is  the  solution  used  for  ?  How  is  common  lime 
prepared  ?  553.  What  is  the  cause  of  the  strength  of  mortar  ?  What 
is  hydraulic  lime  ?  What  is  said  of  the  agricultural  use  of  lime  ? 


CALCIUM.  305 

naturally  in  every  fertile  soil,  and  is  a  constant  ingredient  in 
the  ashes  of  most  plants. 

554.  Chlorid  of  Calcium,  CaCl.— The  solution  of  lime 
or  its  carbonate  in  hydrochloric  acid  to  saturation,  gives  us 
this  salt.     It  is  when  fused  a  white  crystalline  solid,  wkh  a 
great  avidity  for  moisture,  and  for  this  reason  it  is  used  in  the 
desiccation   of  gases,    &c.     It   is   soluble   in  alcohol,  with 
which  it  forms  a  definite  crystallizable  compound.     It  forms 
a  powerful  freezing  mixture  with  ice,  (111.) 

The  sulphurets  and  phosphurets  of  calcium  have  little  in- 
terest. The  phosphuret  being  decomposed  by  water,  is  an 
available  source  of  the  spontaneously  inflammable  phosphu- 
reted  hydrogen. 

555.  Sulphate  of  Lime — Gypsum — Selenite,  CaO,  SO3. 
—This  salt  in  the   form   of  hydrate  (CaO,SO3-f  2HO)  is 
abundant  in  nature,  and  is  much  used  in  agriculture  as  a 
manure,  being   ground  to  powder,  and   after   expelling  the 
water  by  heat,  as  a  material  for  stucco  and  plaster  casts. 
It   is  then  commonly  known  as  '  plaster  of  Paris.'     When 
crystallized  in  transparent  flexible  plates,  it  is  called  selenite. 
Anhydrous  gypsum  also  is  sometimes   found   native,  and  is 
known  by  the  mineralogical  name  of  anhydrite.     Gypsum  is 
frequently  associated  with   rock-salt.     It  is  soluble  in  about 
500  parts  of  water,  and  is   present  in  most  natural  waters. 
By  a  heat  of  200°  to  300°  it  loses  its  water  of  composition, 
and  when  the  anhydrous  powder  is  moistened,  the  lost  water 
is  regained,  and  it  becomes  solid  ;  but  if  overheated,  this  re- 
sult does  not  happen. 

556.  Fluorid  of  Calcium — Fluor    Spar,  CaF. — This  is 
a  rather  abundant  mineral,  being  found  beautifully  crystalliz- 
ed of  various  colors,  in  the  cube  and  its  modifications.     It  is 
the  principal  source  from  which  we  obtain   the  hydrofluoric 
acid,  (425,)   by  decomposition  with   sulphuric  acid.     It  often 
phosphoresces  very  beautifully  with  heat,  and  emits  a  green, 
yellow,  or  purple  light,  at  a  temperature  below  redness. 

557.  Phosphates  of  Lime. — There  are  several  phosphates 
of  lime  corresponding  to  the  several  phosphoric  acids,  (320, 

554.  What  is  the  chlorid  of  calcium  ?  For  what  is  it  used  ?  What 
is  the  phosphuret  of  calcium  used  for  ?  555.  Give  the  common 
names  of  sulphate  of  lime.  For  what  is  it  used  ?  Give  its  proper- 
ties. On  what  does  its  use  in  stucco  depend  ?  556.  What  is  fluor 
spar  ?  How  is  it  found  ?  For  what  used  ?  What  beautiful  property 
has  it  ?  557.  What  phosphates  of  lime  are  known  ? 
26* 


306  METALLIC   ELEMENTS. 

325.)  The  earth  of  bones  is  a  tribasic  phosphate  of  lime, 
and  the  mineral  known  as  apatite  is  also  a  phosphate  of  lime. 
The  phosphates  of  lime  are  insoluble  in  water,  but  dissolve  in 
dilute  acids.  All  cereal  grains,  and  many  other  vegetables, 
contain  phosphate  of  lime  in  their  ashes. 

558.  Carbonate   of  Lime — Marble — Calcareous   Spar, 
CaO,  CO2. — This  is  one  of  the  most  abundant  minerals  of 
the   earth,  forming   in  limestone  vast  mountains    and  wide 
spread  geological  deposits.     It  occurs  most  superbly  crystal- 
lized in  rhombohedral  forms,  which  constitute  brilliant  orna- 
ments   in   mincralogical  collections.     It  is  soluble  in  dilute 
acids,  with  escape  of  carbonic  acid,  and  is  also  decomposed 
by  heat,  (552,)  leaving  quick-lime. 

559.  Chlorid  of  Lime — Bleaching- Powder. — This  valu- 
able compound  is  formed  when  chlorine  gas  is  gradually  ad- 
mitted to  hydrate  of  lime  slightly  moist  and  kept  cool.     The 
chlorine  is  absorbed  largely,  and   the  bleaching-powder  of 
the  arts  is  formed.     It  is  a  soft  white  powder,  easily  soluble 
in  about  10  parts  of  water,  giving  a  highly  alkaline  solution, 
which  bleaches  feebly.     It  is  employed  by  dipping  the  goods 
in  a  weak  solution  of   chlorid   of   lime,  and    then  in  very 
dilute  sulphuric  acid.     The   chlorine   is    thus   evolved    and 
docs  its  work.     Several  repetitions  are  needed  to  complete  the 
process.     This   compound   emits    a  strong  smell,  which  is 
similar   to   chlorine,  but   is   due   to   hypochlorous  acid  ;    it 
is  very  useful  for  disinfecting  offensive  apartments,  and  its 
energy  is  increased  by  the  addition  of  a  little  acid.     The  dis- 
infecting liquid  of  Labarraque  is  a  compound  of  chlorine  with 
soda,  similar  in  composition  to  solution  of  bleaching-powder. 

The  chlorid  of  lime  is  now  known  to  be  a  mixture  of  chlo- 
rid of  calcium  and  hypochlorite  of  lime,  (267.) 

22.    MAGNESIUM. 

Equivalent,  12-67.     Symbol,  Mg. 

560.  Magnesium  is  obtained  by  decomposing  the  chlorid 
of  that   metal  heated  to  redness  in  a  glass  tube,  by  passing 

In  what  do  we  find  phosphate  of  lime  ?  558.  What  is  said  of  car- 
bonate of  lime  ?  What  other  names  has  it  ?  What  is  formed  from 
it  ?  559.  What  is  bleaching-powder  ?  How  formed  ?  How  employ- 
ed ?  What  is  Labarraque's  liquor  ?  What  is  the  known  composi- 
tion of  bleaching-powder  ?  560.  Give  the  equivalent  and  prepara- 
tion of  magnesium. 


MAGNESIUM.  307 

over  it  the  vapor  of  potassium  or  sodium.  Chlorid  of  potas- 
sium or  sodium  is  formed,  and  the  metallic  magnesium  is 
separated  by  dissolving  out  the  soluble  chlorid. 

It  is  a  white  metal,  malleable  and  brilliant.  It  fuses  with 
a  red  heat,  and  if  heated  to  redness  in  the  air,  burns  with  a 
brilliant  light,  becoming  oxyd  of  magnesium.  It  does  not 
tarnish  in  the  air,  and  does  not  decompose  water  even  at 
212°,  but  dissolves  in  acids  with  escape  of  hydrogen. 

561.  Oxyd  of  Magnesium — Calcined  Magnesia,  (MO.) 
— This  substance  is  left  when  the  carbonate  of  magnesia  is 
heated  to  redness.     It  is  a  white,  earthy  powder,  insoluble  in 
water,  but  readily  dissolves  in  weak  acids.     It  occurs   in 
nature    crystallized    in    regular   octahedrons,    forming    the 
mineral  periclase.     It  is   much  used  in  medicine  as  a  mild 
and  efficient  aperient.     The  hydrate  of  magnesia  (MgO,HO) 
is  formed  when  magnesia  is   precipitated  from  its  solutions 
by  an  alkali.     Heat  expels  the  equivalent  of  water.     The 
hydrate  is  found  beautifully  crystallized  in  thin  pearly  plates 
at  Hoboken,  New  Jersey. 

562.  Chlorid  of  Magnesium,  (MgCl.) — This  salt  is  best 
prepared  by  neutralizing  equal  portions  of  hydrochloric  acid, 
one  with  magnesia  and  the  other  with  ammonia,  mixing  the 
two  portions  and  evaporating  to  dryness.     The  dry  mass  is 
heated  in  a  covered  crucible  as  long  as  sal  ammoniac   is 
given  off,  when  pure  chlorid  of  magnesium  is  left.     It  is  a 
very  deliquescent  salt,  and  supplies  the  means  of  procuring 
metallic  magnesium.     When  magnesia  is  dissolved  in  hydro- 
chloric acid,  a  hydrated  chlorid  of  magnesium   results.     By 
heat  the  water  is  expelled,  carrying  with  it  hydrochloric  acid, 
and  leaving  pure  magnesia  behind.     Chlorid  of  magnesium 
exists  in  sea-water.     The  iodid   and   bromid   of  magnesium 
are  also  soluble  salts,  but  the  fluorid  is  insoluble. 

563.  Sulphate  of  Magnesia — Epsom   Salts,  (MgO,  SO3 
-f-  7HO.) — This  well  known   salt   is   easily   formed    by  dis- 
solving magnesia  or  its  carbonate  in  sulphuric  acid.     It  is 
also  found  native  at  Corydon,  Illinois.     It  is  made  on  a  large 
scale  by  dissolving  serpentine  rock  in  strong  sulphuric  acid. 


What  are  its  properties  ?  561.  What  is  the  oxyd  of  magnesium  ? 
How  is  it  used  ?  How  found  in  nature  ?  562.  How  is  the  chlorid 
of  magnesium  prepared  ?  Describe  it.  When  magnesia  is  dissolved 
in  hydrochloric  acid,  what  happens  ?  563.  What  is  the  composition 
of  sulphate  of  magnesia  ?  How  is  it  made  in  the  large  way  ? 


308  METALLIC    ELEMENTS. 

It  is  very  soluble,  and  like  all  the  soluble  salts  of  magnesia, 
has  a  peculiar  bitter  taste. 

564.  The  Carbonate  of  Magnesia  is  found  native  in  mag- 
nesian  rocks,  and  is  formed  artificially  by  decomposing  any 
of  the  soluble  salts  of  magnesia   by  an  alkaline  carbonate. 
It  is  insoluble  in  water;  but  a  solution  of  carbonic  acid  dis- 
solves it,  and   forms  the  celebrated   Murray's  solution  of 
magnesia  ;  it  is  decomposed  by  contact  of  air,  carbonic  acid 
escapes,  and  carbonate  of  magnesia  is  thrown  down. 

Phosphate  of  soda  with  ammonia  throws  down  a  crystalline 
insoluble  salt  from  magnesian  solutions,  which  is  the  double 
phosphate  of  magnesia  and  ammonia.  This  is  the  most 
ready  mode  of  testing  for  the  presence  of  magnesia. 

565.  Magnesia  occurs   abundantly   in    nature  as  a  con- 
stituent of  many  minerals,  as  well  as  in  the  form  of  hydrate 
and  carbonate.     It  is  present  in  nearly  all   fertile  soils,  and 
constitutes  an  important  part  of  the  inorganic  matters  in  the 
husk  and   seeds  of    many   plants.      The  potato   especially 
contains  a  large  portion  of  the  ammonio-phosphate  of  mag- 
nesia, and   hence  bran  is  a   useful   manure  for  the  potato, 
because  it  is  peculiarly  rich  in  this  salt. 


CLASS  TIL— METALS  OF  THE  EARTHS. 

23.    ALUMINIUM.    AL.  =  13'69. 

566.  Aluminium  is  best  obtained,  like  magnesium,  by  the 
action  of  sodium  or  potassium  on  its  chlorid.     It  is  a  gray 
powder,  not  easily  melted,  has  a  metallic  lustre,  and    burns 
when  heated  in  the  air  with  a  bright  light,  forming  alumina. 

567.  Alumina  ;    Sesquioxyd   of   Aluminium  ;    A12O3. — 
Pure  alumina  is  found  crystallized  in   those  precious   gems, 
the  oriental  ruby  and   sapphire,  which  are  next   in  hardness 
and  value  to  the  diamond.     Emery  is  also  nearly  pure  alu- 
mina.    Alumina   is  an  abundant  ingredient   in  many  other 
minerals,  and  forms  a  large  part  of  many  slaty  rocks,  from 
whose  decomposition  clays  are  produced. 


564.  What  is  carbonate  of  magnesia  ?  What  is  Murray's  solution  ? 
What  test  have  we  for  magnesia  /  565.  How  does  magnesia  occur 
in  nature  ?  In  what  plants  is  it  found  ?  566.  How  is  alumina  ob- 
tained ?  What  are  its  properties  ?  567.  What  is  the  formula  of 
alumina  ?  In  what  is  it  found  pure  ? 


ALUMINA.  309 

Pure  alumina  is  a  fine  white  powder,  not  rough  and  gritty 
like  silica  ;  mixed  with  water  it  forms  a  plastic  mass,  which 
has  the  well  known  tenacious  qualities  of  clay.  It  is  the 
basis  of  the  art  of  pottery.  When  alumina  is  precipitated 
from  its  solutions  in  acids  by  an  alkali,  it  falls  as  a  bulky, 
gelatinous,  transparent  hydrate,  which  shrinks  very  much  on 
drying,  and  has  three  equivalents  of  water  of  composition  at 
100°,  which  are  expelled  by  heat.  The  anhydrous  alumina 
is  almost  insoluble  in  acids,  while  the  hydrate  is  readily  dis- 
solved, forming  salts  of  a  peculiar  astringent  taste,  familiarly 
known  in  common  alum. 

Alumina  is  precipitated  as  a  hydrate  from  solution,  by 
either  potash,  soda,  or  ammonia,  and  their  carbonates  ;  an 
excess  of  the  two  first  will  redissolve  the  precipitate.  Hy- 
drosulphuret  of  ammonia  throws  down  alumina.  The  chlorid 
of  aluminium  has  no  particular  interest  except  as  a  means  of 
procuring  the  metal. 

568.  Sulphate  of  Alumina,   A12O33SO3+18HO.  — This 
salt   is   prepared   by  saturating  dilute  sulphuric  acid   with 
alumina ;  it  has  a  sweetish  astringent  taste,  is  soluble  in  2 
parts  of  water,  and  crystallizes  in  thin  plates. 

Alums. — Sulphate  of  alumina  forms  with  potash,  soda, 
and  ammonia,  double  salts  of  much  interest,  called  alums. 
They  are  all  soluble  salts,  with  a  sweetish  astringent  taste, 
and  crystallize  in  the  regular  system,  or  first  class,  (220,) 
usually  as  modified  octahedrons,  which  have  uniformly  24 
equivalents  of  water  of  crystallization.  Common  potash-alum 
has  the  formula  Al2O3>3SO3  +  KO,SO3-f  24HO,  (205;)  it 
dissolves  in  18  parts  of  cold  water,  and  the  solution  has  an 
acid  reaction. 

569.  Alum  and  Acetate  of  Alumina  are  largely  employed 
in  the  arts  of  dyeing  and  tanning.     Alumina  combines  with 
coloring  matters,  and  seems  to  form  a  bond  of  union  be- 
tween the  fibre  of  the  cloth  and  the  color.     In  this  it  is  said 
to  act  the  part  of  a  mordant.     When  alum  is  added  to  the 
solution  of  a  coloring  matter,  and  the  alumina  is  precipitated 
with  an  alkali,  all  the  coloring  matter  is  thrown  down  with 

What  are  its  properties  ?  How  is  its  hydrate  described  ?  What 
difference  is  there  in  the  two  forms  of  alumina  ?  How  is  alumina 
distinguished  by  tests  ?  568.  What  is  the  sulphate  of  alumina  ? 
What  are  alums?  Give  the  formula  of  common  alum.  569.  In 
what  art  is  alum  much  used  ?  How  does  it  act  with  colors  ?  What 
are  lakes  ? 


310  METALLIC    ELEMENTS. 

it  and  forms  what  is  called  lake.  The  common  lake  used 
in  water-coloring  is"  derived  from  madder  treated  in  this  way. 
Carmine  is  a  lake  made  from  cochineal. 

570.  Silicates  of  Alumina. — This  is  the  most  extensive 
and  important  class  of  the  aluminous  salts,  and  comprises  a 
great  number  of  interesting   minerals.     Feldspar,  (A12O3, 
«3SiO3-r-KO,SiO3,)  which  is  one  of  the  chief  components  of 
granite  and  granitic  rocks,  is  of  this  class,  and  has  the  com- 
position of  an  anhydrous  alum,   the   sulphuric  acid   being 
replaced  by  the  silicic.     Kyanite  and  Sillimanite  are  simple 
basic  silicates  of  alumina.     Albite  is  a  salt  having  soda  in 
place  of  the  potash  in  feldspar,  while  spodumene  and  petalite 
are  similar  compounds,  with  a  portion  of  the  soda  replaced 
by  lithia.     Many  other  similarly  constituted  compounds  are 
found  among  minerals,  some  of  which  are  hydrous  and  others 
anhydrous,  and  varied  by  frequent  substitution  of  peroxyd  ot 
iron,  or  other  isomorphous  bases,  for  the  alumina. 

571.  Pottery. — The  decomposition  of  feldspar  and  other 
aluminous   minerals  and    rocks,  gives  origin    to  the  clays 
which  are  so  important  in  the  art  of  pottery.     Decomposed 
feldspar  forms  porcelain  clay,  commonly  called  kaolin.    The 
undecomposed   mineral   is  often   ground  up  to  mix  with  the 
materials   for  porcelain.     The   feldspar  of  Middletown,  Ct., 
and   Wilmington,  Delaware,  is  used   in  large  quantities  for 
this  purpose. 

The  difference  between  porcelain  and  earthen  ware,  con- 
sists in  the  partial  fusion  of  the  materials  of  the  former  by 
the  heat  of  the  furnace,  which  gives  it  the  semi-transparency 
and  great  beauty  for  which  it  is  so  highly  prized.  The 
glaze  in  porcelain  is  formed  of  a  more  fusible  mixture  of  the 
same  materials,  put  over  the  articles  as  a  wash,  after  they 
have  been  once  through  the  furnace ;  (in  which  state  they 
are  called  biscuit  ware ;)  they  are  then  baked  again  at  a  heat 
which  fuses  the  glaze,  but  which  does  not  soften  the  body  of 
the  ware. 

572.  The  painting  of  porcelain  is  an  art  requiring  a  refined 
knowledge  of  chemistry.     All  the  colors  used  in  this  art  are 


570.  What  is  the  most  important  class  of  alumina  compounds  ? 
Give  the  composition  and  properties  of  feldspar.  571.  What  is  the 
origin  and  composition  of  clays  ?  Of  what  material  is  porcelain 
composed  ?  How  does  it  differ  from  earthen  ware  ?  Of  what  does 
the  glaze  consist  ? 


GLUCINCM,    YTTRIUM,    &C.  311 

metallic  oxyds,  which  are  put  on  after  the  ware  has  been 
once  baked.  The  colors  result  from  compounds  formed  by 
the  metallic  oxyds  with  alumina  by  fusion,  and  do  not  ap- 
pear until  after  the  baking.  Metallic  gold  is  put  on  in  the 
form  of  an  oxyd,  and  the  steel  lustre  is  produced  by  metal- 
lic platinum. 

24.    GLUCINUM.  25.    YTTRIUM.  26.    ZIRCONIUM. 

27.    THORIUM.  28.    CERIUM.  29.    LANTANUM. 

573.  All  these  metals  are  so  rare  as  to  be  known  only  to 
chemists.  Their  oxyds  occur  in  several  minerals,  nearly  all 
of  which  are  among  the  most  uncommon  specimens  in  min- 
eralogical  collections.  Glucina,  (24,)  or  the  sesquioxy,d  of 
glucinum,  (G2O3,)  is  the  most  abundant,  being  found  to  the 
amount  of  17  per  cent,  in  the  gems,  beryl,  emerald,  and 
chrysoberyl.  It  very  much  resembles  alumina,  and  is 
named  in  allusion  to  the  sweet  taste  of  its  salts.  Yttria,  (25,) 
the  oxyd  of  yttrium,  (YO,)  is  a  white  earthy  powder,  form- 
ing sweetish  salts,  but  differing  from  alumina  and  glucina  in 
not  being  redissolved  like  them  in  an  excess  of  potash  and 
soda  :  this  earth  is  found  in  the  minerals  yttro-cerite,  gadoli- 
nite,  and  yttro-tantalite.  Zirconia,  (26,)  sesquioxyd  of  zir- 
conium, (Zr2O3,)  which  is  the  earth  of  the  zircon  or  hyacinth, 
much  resembles  alumina,  but  differs  from  it  and  from  gluci- 
cina,  yttria,  and  thorina,  by  being  precipitated  from  its 
solutions,  as  an  insoluble  sulphate,  by  boiling  with  solution 
of  sulphate  of  potash.  Thorina,  (27,)  the  oxyd  of  thorium, 
is  found  in  only  one  or  two  very  rare  minerals,  as  in  thorite 
and  monazite ;  its  specific  gravity  is  9,  being  much  higher 
than  any  other  earth.  Cerium,  (28,)  and  Lantanum,  (29.) — 
The  oxyds  of  these  two  rare  metals  are  invariably  associated 
with  each  other,  and  also  with  that  of  another  metal,  didy- 
mium,  not  yet  fully  described ;  they  are  found  only  in  some 
very  rare  minerals,  as  cerite,  allanite,  monazite,  &c.  The 
oxyd  of  cerium  forms  beautiful  yellow  salts,  while  the  oxyd 
of  lantanurn  forms  equally  beautiful  rosy  compounds  ;  the 
latter  has  been  named  in  allusion  to  its  having  been  long  con- 
cealed or  hidden  under  cerium,  with  which  it  is  associated. 


572.  How  is  porcelain  colored  ?  573.  What  six  metals  included 
in  this  section  ?  In  what  mineral  is  glucina  found  ?  Describe  yttria. 
In  what  mineral  is  zirconia  found  ?  What  are  its  properties  ?  What 
is  said  of  thorium  ?  With  what  is  cerium  always  associated  ? 


312  METALLIC    ELEMENTS. 

CLASS  IV.    METALS  WHOSE  OXYDS  FORM  POWERFUL 
BASES. 

30.    MANGANESE. 

Equivalent^  27-67.     Symbol,  Mn.     Density,  8. 

574.  Manganese  is  never  found  as  a  metal  in  nature,  but 
may  be  produced  from  its  black  oxyd   by  a  high   heat  with 
charcoal.     Metallic  manganese  is  a  gray  brittle  metal,  not 
magnetic,  and  resembles  some  varieties  of  cast  iron.     It  dis- 
solves rapidly  in  sulphuric  acid  with  escape  of  hydrogen. 

Manganese  in  the  form  of  the  black  oxyd  is  an  important 
and  pretty  common  metal.  Its  great  use  is  for  producing 
chlorine,  (260,)  and  in  the  manufacture  of  glass,  where  it 
acts  by  its  oxygen  to  decolorize  the  compound. 

575.  The  oxyds  of  manganese  are  numerous  ;  we  give 
the  formulas  of  six,  and  there  are  possibly  one  or  two  more, 
viz :    protoxyd,   MnO ;    sesquioxyd,  (or   braunite,)   Mn2O3 ; 
peroxyd,  or  deutoxyd,  (pyrosulite,)  MnO2;  red  oxyd,  (haus- 
mannite,)   Mn3O4 ;    manganic  acid,   Mn03 ;  hypermanganic 
acid,  Mn2O7. 

The  Protoxyd  is  a  green-colored  powder,  formed  from 
heating  the  carbonate  of  manganese  in  hydrogen.  It  is  a 
powerful  base,  attracts  oxygen  from  the  air,  and  is  the  base 
of  the  beautiful  rose-colored  salts  of  manganese. 

The  sesquioxyd  or  braunite  occurs  crystallized  in  octahe- 
drons, and  forms  belonging  to  the  dimetric  system. 

The  Hydrated  Sesquioxyd  (manganite)  is  a  finely  crystal- 
lized mineral  in  long  black  prisms,  found  in  superb  speci- 
mens at  Ilfeld,  in  the  Hartz.  In  powder  the  sesquioxyd  is 
brown  ;  it  is  decomposed  by  hydrochloric  acid  with  the  evo- 
lution of  chlorine,  but  sulphuric  acid  combines  with  it  to  form 
a  sesquisulphate,  which  yields  a  purple  double  salt  with  sul- 
phate of  potash,  (manganese  alum,)  isomorphous  with  the 
corresponding  salt  of  alumina.  This  salt  is,  however,  very 
easily  decomposed  by  a  gentle  heat. 

574.  What  is  said  of  manganese  ?  What  form  of  it  is  most  com- 
mon ?  For  what  is  it  used  ?  575.  How  many  and  what  oxyds  of 
manganese  are  named  ?  Which  is  the  base  of  the  rose-colored  salts  ? 
What  is  the  sesquioxyd  ?  What  is  the  hydrated  sesquioxyd  ?  What 
is  said  of  the  sulphate  of  the  sesquioxyd  ? 


MANGANESE.  313 

576.  The  Perosyd  is  the  most  common  ore  of  manganese, 
and  has  a  high  commercial  value.     It  is  found  abundantly  at 
Bennington,  Vt.,  and  other  places  in  this  country.     When 
crystallized  it  is  called  pyrolusite,  and  beautiful  specimens  of 
this  mineral  have  been  observed  at  Salisbury  and  Kent,  Conn., 
among  the  iron  ores. 

577.  Manganic  Acid  is  known  only  in  combination,  gen- 
erally as  manganate  of  potash.    This  is  best  formed  by  mixing 
equal  parts  of  finely  powdered  black  oxyd  of  manganese  and 
chlorate  of  potash  with  rather  more  than  one  part  of  hydrate 
of  potash  dissolved  in  a  very  little  water.         This  mixture 
when  evaporated  is  heated  to  a  point  short  of  redness,  and  a 
dark  green  mass  is  formed  which  contains  manganate  of  potash. 
In  this  case  the  manganese  obtains  oxygen  from  the  chlorate 
of  potash,  and  the  manganic  acid  thus  formed  combines  with 
potash,  giving  a  salt  in  green  crystals.     This  salt,  dissolved 
in  water,   gives   a   brilliant   emerald-green   solution,  which 
almost  immediately  changes  color,  being  in  quick  succession 
green,  blue,  purple,  and  finally  crimson-red,  and   has  thence 
been  called  chameleon  mineral.     This  last  color  is  due  to 
the  presence  of  permanganic  acid,  which,  however,  cannot 
be  separated  from  its  combinations,  but  forms  a    salt  with 
potash  in  beautiful  purple  crystals.     The  compounds  of  per- 
manganic acid  are  more  stable  than  the  manganates.     The 
salts  of  these  acids  are  respectively  isomorphous  with  sul- 
phates and  perchlorates,  (SO3  and  CI2O7.) 

578.  The  chlorids  of  manganese   (MnCl  and    Mn2Cl3) 
correspond  to  the  protoxyd  and  sesquioxyd.     The  chlorid  is 
formed   abundantly  in  acting  on  black  oxyd  of  manganese, 
(260,)  with  hydrochloric  acid.     The  mixed  solution  of  chlo- 
rids of  iron  and   manganese  is  evaporated   to  dryness,  and 
then  heated  to  dull  redness.     The  chlorid  of  manganese  is 
then  dissolved  out  from  the  dry  mass,  leaving  the  insoluble 
protoxyd  of  iron  behind.     It  has  a  beautiful  pink  tint,  and 
deposits  tabular  rose-colored  crystals  on  evaporation.     It  is 
soluble  in  alcohol,  and   fusible  by  heat.     The  sesquichlorid 
is  formed  by  solution  of  sesquioxyd  in  cold  hydrochloric  acid, 
but  is  decomposed  by  a  gentle  heat  and  evolves  chlorine. 


576.  Which  is  the  most  common  ore  of  manganese  ?  Where  and 
how  is  it  found?  577.  Describe  manganic  acid  and  the  curious  salt 
it  forms  with  potash.  What  is  the  changeable  compound  called  ? 
What  is  said  of  the  salts  of  manganic  and  permanganic  acid  ?  578. 
Describe  the  chlorids  of  manganese. 
27 


314 


METALLIC    ELEMENTS. 


579.  The  salts  of  manganese  are  numerous,  and  in  a 
chemical  view  quite  important.  Sulphate  of  manganese  is 
a  very  beautiful  rose-colored  salt,  isomorphous  with  sulphate 
of  magnesia.  It  is  used  to  give  a  fine  brown  dye  to  cloth, 
being  decomposed  by  a  solution  of  bleaching-powder,  which 
forms  the  brown  peroxyd  in  the  fibre  of  the  stuffs. 

31.     IRON. 
Equivalent,  27.14.     Symbol,  Fe.     Density,  7*8. 

590.  Iron  is  found  mallcabh,  and  alloyed  with  nickel,  in 
large  masses  of  meteoric  origin.  One  of  these,  discovered  in 
Texas,  weighs  1635  pounds,  and  is  now  in  Yale  College 
Cabinet.  It  is  not  certain  that  malleable  iron  of  terrestrial 
origin  has  yet  been  discovered  -in  nature.  Iron  is  the  most 
abundant  and  most  important  metal  known  to  man.  Its  ores 
are  found  everywhere,  and  often  in  immediate  connection 
with  the  coal  and  limestone  necessary  to  reduce  them  to  the 
metallic  state.  There  is  no  soil,  and  scarcely  any  mineral, 
which  does  not  contain  some  proportion  of  the  oxyd  of  iron. 

581.  Pure  iron  is  difficult  to  prepare.  The  purest  iron  of 
commerce  is  always  contaminated  with  a  portion  of  silicon 
and  carbon.  When  quite  pure  it  is  nearly  white,  quite  soft, 
perfectly  malleable,  and  the  most 
tenacious  of  all  metals.  Its  density 
is  7*8,  which  may  be  a  little  in- 
creased by  hammering.  It  crystal- 
lizes in  forms  of  the  first  class,  as  is 
beautifully  shown  in  the  crystalline 
structure  of  the  meteoric  iron.  It  fuses 
with  extreme  difficulty,  first  becom- 
ing soft  or  pasty,  in  which  state  it  is 
welded.  When  intensely  heated  in 
air  or  oxygen  gas  it  combines  with 
oxygen,  burning  with  brilliant  light 
and  numerous  scintillations,  and  is 
converted  into  oxyd  of  iron,  (255.)  Iron  also  attracts  oxy- 
gen at  common  temperatures,  forming  rust.  This  does  not 

579.  What  is  said  in  general  of  the  salts  of  manganese  ?  580. 
What  is  the  equivalent  of  iron  ?  How  is  malleable  iron  found  ? 
What  is  said  of  its  abundance  and  value  ?  581.  Give  the  properties 
of  iron.  What  is  said  of  its  fusion  and  welding?  How  does  it  be- 
have with  oxvcen  ? 


IRON. 


315 


happen  in  dry  air,  but  the  presence  of  moisture,  and  particu- 
larly of  a  little  acid  vapor,  very  much  promotes  its  formation. 
Iron  decomposes  water  very  rapidly  at  a  red  heat,  hydrogen 
being  evolved.  It  is  the  chief  medium  of  magnetism,  being 
powerfully  attracted  by  the  magnet,  and  also  itself  suscepti- 
ble of  this  influence. 

582.  The  chief  ores  of  iron   are,  (1,)  brown  hematite  or 
hydrous  peroxyd,  from  which  the  best  iron  is  made.     (2.) 
The  red  hematite  and  specular  iron  or  peroxyd.     (3.)  Clay 
iron  stone,  which  is  an  impure  carbonate  of  iron,  or  carbon- 
ate of  iron  with  carbonate  of  lime  and  magnesia.     This  is 
the  nodular  ore  of  the  coal  formations.     (4.)  Black  or  mag- 
netic oxyd  of  iron,  which  is  the  ore  of  the  iron  mountains 
of  Missouri  and  of  Sweden. 

583.  The  reduction  of  the  ores  of  iron  to  the  metallic 
state  is  performed  in  large  furnaces  called  high  or  blastfur- 
naces.    These  are  built  of  stone, 

in  a  conical  form,  30  to  50  feet 

high,  and  lined  internally  with 

the   most  refractory  fire-bricks. 

The  furnace  is  divided  into  the 

throat,   the   fire-room,   (6,)   the 

boshes,  (e,)  (that  portion  sloping 

inward,)  the  crucible,  (£,)   and 

the  hearth,  (h.)     The  blast  of 

air  —  supplied   from  very  large 

blowing  cylinders — is  introduced 

by  two  or  three  tuyere  pipes  (aa) 

near  the  bottom.     In  the  most 

improved  furnaces,  the  air-blast 

is  heated  by  causing  it  to  pass  a\ 

through  a  series  of  pipes  in  the 

upper  portion  of  the  furnace,  so 

as  to  have  a  temperature  of  500°  or  more  when  it  enters  the 

furnace.     When  the  furnace  is  brought  into  action,  it  is  first 

heated  with  coal  only,  for  about  24  hours  ;  and  then  is  charged 

alternately  with  proper  proportions  of  coal,  roasted  ore,  and 

lime  for  flux,  until  it  is  quite  full.     When  once  brought  into 

action,  the  blast  is  kept  up  for  months  or  even  years,  until 


582.  What  ores  of  iron  are  enumerated  ?  583.  How  is  the  reduc- 
tion of  iron  effected  ?  Describe  the  high  furnace.  What  is  the  hot 
blast  ? 


316  METALLIC    ELEMENTS. 

the  furnace  requires  repairing.  The  ore  is  reduced  on  the 
boshes,  and  in  the  upper  part  of  the  crucible,  and  the  melted 
metal  collects  on  the  hearth,  covered  by  the  molten  flux, 
which  is  a  glass  formed  by  the  fusion  of  the  lime  used  and  the 
earthy  parts  of  the  ore.  From  time  to  time,  the  iron  is 
drawn  olF  by  an  opening  previously  stopped  with  clay,  and 
run  into  rude  open  moulds  in  sand.  This  is  cast  iron,  and 
is  of  various  qualities,  according  the  various  character  of  the 
ore,  and  the  working  of  the  furnace.  If  malleable  bar  iron  is 
wanted,  the  cast-iron  is  again  melted,  in  what  is  called  the 
puddling  furnace,  where  it  is  stirred  about  by  an  iron  rod,  in 
contact  with  oxyd  of  iron,  and  a  current  of  heated  carbonic 
oxyd  from  the  high  furnace.  It  gradually  becomes  stiff  and 
pasty  from  the  burning  out  of  the  carbon,  and  from  some 
molecular  change  not  well  understood.  It  is  finally  raised  in 
a  rude  ball  and  placed  under  the  blows  of  a  huge  tilt-hammer, 
when  the  scoria  is  pressed  out  and  the  particles  made  to 
cohere.  It  grows  tenacious  by  a  repetition  of  this  process, 
being  cut  up  and  piled  or  faggoted  and  reheated  several 
times,  until  it  is  finally  made  into  tough  and  fibrous  metal. 

584.  Steel  is  formed  from  refined  iron  by  heating  in  con- 
tact with  charcoal   in  close  vessels,  (called  cementation.)     It 
gains  from  one  to  two  per  cent,   of  carbon,  becomes  fusible, 
and   can   be  tempered  according  to  the  use  for  which  it.  is 
designed. 

585.  The  oxyds  of  iron  are  four,  viz:  (1,)  protoxyd, 
(FeO;)  (2,)  sesquioxyd,  commonly  called  peroxyd,  (FejOa ;) 
(3,)  black  oxyd,  (magnetic  oxyd,)  (Fe3O4,)  and  (4)  ferric  acid, 
(Fc03.) 

(1.)  The  Protoxyd  of  Iron  is  a  powerful  base  which  is 
unknown  in  nature  except  in  combination.  It  saturates 
acids  completely  and  is  isomorphous  with  a  large  class  of 
bodies,  of  which  zinc  and  magnesia  are  examples,  (232.) 
This  oxyd  is  thrown  down  from  its  solutions  by  potash,  as  a 
whitish  bulky  hydrate,  that  soon  gains  another  dose  of  oxy- 
gen from  the  air  becoming  brown,  and  finally  red.  Its  salts 
when  soluble  have  a  styptic  taste  like  ink  and  a  greenish 
color. 


What  is  the  operation  of  the  furnace  ?  What  is  cast  iron  ?  How 
is  malleable  iron  made  from  cast  iron  ?  584.  What  is  steel  ?  585. 
What  are  the  oxyds  of  iron  ?  Give  their  formulas.  Describe  the 
protoxyd. 


IRON.  317 

586.  (2.)   The  Peroxyd  of  Iron  is  found    native  in  the 
beautiful    specular  iron  of  Elba,  and  also  in  the  red   and 
brown  hematites.     It  is  slightly  acted  on  by  the  magnet,  and 
after  ignition  is  almost  insoluble  in  strong  acids.     It  is  iso- 
morphous  with  alumina,  and  is  generally  associated  with  it  in 
soils  and  many  minerals.     It  is  often  of  a  brilliant  red,  and 
as  ochre  of  various  tints  is  much  used  as  a  pigment.     Am- 
monia precipitates  it  from  its  solutions  as  a  bulky  red  hydrate. 

587.  (3.)  Black  Oxyd  of  Iron  is  familiarly  known  in  the 
common  magnetic  iron  ore  and  native  lode-stone.     It  crystal- 
lizes in  octahedrons.     It  forms  no  salts.     The  fiery  cinders 
or   scales   thrown   off  under   the   smith's  hammer  are  this 
oxyd. 

(4.)  Ferric  Acid  is  a  new  compound,  corresponding  to 
manganic  acid,  discovered  by  M.  Fremy.  A  ferrate  of  pot- 
ash is  formed,  when  one  part  peroxyd  of  iron  and  four  parts  of 
nitre  are  heated  to  full  redness  in  &  covered  crucible  for  an 
hour.  The  ferrate  of  potash  is  dissolved  out  of  the  porous 
mass  by  ice-cold  water.  The  solution  has  a  deep  amethys- 
tine color,  and  is  easily  decomposed  by  heat.  A  soluble 
salt  of  baryta  precipitates  ferric  acid  as  a  beautiful  red  ferrate 
of  baryta,  which  is  permanent. 

The  chlorids  of  iron  (FeCl  and  Fe2Cl3)  correspond  to  the 
protoxyd  and  sesquioxyd  (peroxyd)  of  the  same  base.  The 
latter  is  often  used  in  medicine  and  may  be  formed  by  satu- 
rating hydrochloric  acid  with  freshly  prepared  peroxyd  of 
iron.  The  protiodid  of  iron  is  also  a  valuable  medicine. 

588.  The  sulphurets  of  iron  are  found  native,  and  are 
well  known  as  pyrites.     The  protosulphuret  is  easily  formed 
artificially,  by  fusing  sulphur  with   iron-filings ;  they  ignite 
with  a  vivid  combustion,  (459,)  and  protosulphuret  of  iron  is 
formed,  which  is  much  used  in  preparing  sulphureted  hydro- 
gen.      Yellow   iron  pyrites   and    white   iron   pyrites   are 
dimorphous  forms  of  the  bisulphuret,  (FeS2 ;)  the  first  is  one 
of  the  most  common  of  crystallized  minerals.     The  mag- 
netic sulphuret,  magnetic  pyrites,  corresponds  in  composition 
to  the  magnetic  oxyd. 


586.  How  is  the  peroxyd  known  ?  587.  What  is  the  black  oxyd  ? 
What  is  ferric  acid  ?  What  chlorids  of  iron  are  named  ?  What 
oxyds  do  they  correspond  to  ?  588.  What  are  the  sulphurets  of  iron  1 
For  what  is  the  protosulphuret  used  ?  What  is  the  name  of  the 
ordinary  sulphuret  ? 
27* 


318  METALLIC    ELEMENTS 


.  Of  the  salts  of  iron,  the  green  rtriol  or  protosul- 
phate  (FeO,  SO3-f  7HO)  is  the  most  important.  It  is  made 
in  immense  quantities,  as  at  Stafford,  Vt.,  from  the  decompo- 
sition of  iron  pyrites,  which  furnishes  both  the  acid  and  the 
base.  This  salt  crystallizes  beautifully,  and  is  much  used  as 
the  basis  of  all  black  dyes  and  ink,  and  in  the  manufacture 
of  prussian  blue.  It  is  called  copperas  in  the  arts.  Persul- 
phate of  iron  is  a  sulphate  of  the  |>ero.\yd,  (Fe-Os  +  tfSOg.) 
Carbonate  of  iron  occurs  in  nature  as  spathic  iron  ore, 
which  is  isomorphous  with  carbonate  of  lime.  A  variety  of 
steel  is  made  directly  from  this  ore  without  cementation, 
(o^-l.)  It  is  formed  artificially  by  precipitating  a  solution  of 
sulphate  by  an  alkaline  carbonate,  and  is  used  in  medicine. 

The  presence  of  a  salt  of  iron  is  easily  detected  by  the 
fine  blue  (prussian  blue)  formed  on  adding  prussiate  of 
potash  to  the  solution  ;  an  infusion  of  galls  gives  a  black 
color  (ink)  to  solutions  of  iron. 

32.  cnROMirM. 
Efimvalent,  28-14.      Symbol,  Cr.     Density,  0. 

590.  Chromium   in   combination   irith  iron   is   rather  an 
abundant  substance,  particularly  in  this  country,  bcin^  Ibund 
as  chromic  iron  at  iinrchills,  near  Baltimore,  Lancaster  Co., 
Pa.,  and   in  other  places.     The   beautiful   red  chromate  of 
lead  is  also  a   natural  product  in  iSil>eria.     The  metal,  from 
its  great  affinity  for  oxygen,  is  very  difficult   to  procure.      It 
is  n  hard,  almost  infusible  substance,  resembling    cast-iron, 
nearly  insoluble  in  acids,  and  does  not  decompose  water.     I 
may  be  oxydizcd   by  fusion  with   nitre,  but  does  not  change 
in  the  air. 

591.  Chromium  forms  five  compounds  with  oxygen;    of 
which  the  sesquioxyd  (Cr2O3)  and  chromic  acid  (CrO,)  are 
the  most  important.     Chromium  bears  the  strongest  analogy 
in  its  chemical  character  to  manganese  and   iron.     The  per- 
fect identity  of  constitution  in  the  oxyds  of  these  three  metals 
is  shown  in  the  following  tabular  arrangement  : 


589.  Which  of  the  salts  of  iron  are  named  as  very  important  ? 
How  and  where  is  it  made  in  this  country  ?  What  is  the  carbonate 
and  for  what  used  ?  590.  Give  the  equivalent  and  symbol  of  chro- 
mium. How  is  it  found  associated?  What  of  the  metal?  591. 
What  compounds  does  chromium  form  with  oxygen  ? 


CHROMIUM.  319 

Acids. 

Protoxyd.      Sesquioxyd.     Black  oxyd. x 

Manganese  forms,  MnO          MmQs          M n3O4         MnOa     Mn2O7. 
Iron  forms,  FeO  Fe2O3  Fe3O4          FeO3 

Chromium  forms,   CrO  CraOa  Cr304          CrO3      Cr2O7. 

The  Protoxyd  of  Chromium  has  only  very  lately  been 
formed  by  M.  Peligot,  and  is  a  strong  base.  It  acts  in  com- 
bination like  the  protoxyd  of  iron,  with  which  it  is  isomor- 
phous. 

592.  The  Sesquioxyd  of  Chromium  is  easily  prepared,  by 
treating  a  boiling  and  rather  dilute  solution  of  bichromate  of 
potash,  with  an  excess  of  hydrochloric  acid,  and  then  with 
small  successive  portions  of  alcohol  or  sugar,  until  it  assumes 
a  fine  emerald   green  tint.     Ammonia  in  slight  excess  will 
now  throw  down  the   hydrated  oxyd  as  a  bulky  pale  green 
precipitate,  soluble  in  acids.     When  this  precipitate  is  dried, 
it  shrinks  very  much,  and  on   ignition   suddenly  undergoes 
a  vivid  incandescence  and  becomes  deep  green.     The  sesqui- 
oxyd  of  chromium  is  a   feeble  base  like  those  of  iron  and 
alumina,  and  may  replace  them  in  combination,  as  in  the  for- 
mation of  chrome  alum  with  sulphate  of  potash.     All   the 
salts  of  this  oxyd  are  either  emerald  green  or  bluish  purple. 
It  imparts  a  rich  tint  of  green  to  glass  and  porcelain,  and  is 
the  cause  of  the  color  of  the  emerald. 

The  Protochlorid  of  Chromium  (CrCl)  is  obtained  as  a 
white  and  very  soluble  substance  by  the  action  of  dry  hydro- 
gen gas  on  the  following  compound.  The  Sesqvichlorid  (Cr2 
C13)  is  prepared  by  passing  chlorine  gas  over  an  ignited  mix- 
ture of  the  sesquioxyd  and  charcoal.  It  forms  a  crystalline 
sublimate  of  a  peach-blossom  color,  and  is  insoluble  in  water. 
The  sesquioxyd  dissolves  in  hydrochloric  acid,  but  the  hydra- 
ted chlorid  thus  obtained  is  decomposed  by  heat. 

593.  Chromic  Acid  (CrO3)  is  readily  formed  by  treating 
a  cold  and  concentrated  solution  of  bichromate  of  potash  with 
one  and  a  half  parts  of  sulphuric  acid.     The  mixture  when 
cold  deposits  brilliant  ruby-red  prisms  of  chromic  acid.     The 
sulphate  of  potash  in  solution   above,  may  be  turned  off,  and 
the  chromic  acid  dried  on  a  porous  brick,  being  carefully 


With  what  metals  is  it  closely  allied  ?  How  is  this  relation 
shown  ?  Give  the  comparative  formulas  of  the  oxyds  of  manganese, 
iron,  and  chromium.  What  is  said  of  the  protoxyd  ?  592.  How  is 
the  sesquioxyd  prepared  ?  What  are  \ts  properties  and  analogies  ? 
593.  How  is  chromic  acid  prepared  *  What  are  its  properties  ? 


320  METALLIC    ELEMENTS. 

covered  with  a  glass  to  prevent  access  of  organic  matters, 
which  at  once  decompose  it.  If  a  little  of  this  acid  bo 
thrown  into  alcohol  or  ether,  the  violence  of  the  action  is 
such  as  to  set  fire  to  the  mixture.  Chromic  acid  forms 
numerous  salts,  which  are  all  highly  colored. 

594.  The  Chromate  of  Potash  and  the  Bichromate  are 
both   familiar  examples.     The  first,  (KG,  CrO3)   is   formed 
on  a  very  large  scale  by  decomposing  the  native  chromic 
iron  with  nitrate  of  potash,  by  aid  of  heat.     Chromate  of 
potash  is  dissolved  out   from  the   ignited   mass,  and  crystal- 
lizes in  anhydrous  yellow  crystals.     It   is   isomorphous  with 
sulphate  of  potash,  dissolves  in  two  parts  of  cold  water,  and 
is  the  source  of  all  the  preparations  of  chromium. 

Bichromate  of  Potash  (KO,  2CrO3)  is  formed  by  adding 
sulphuric  acid  to  a  solution  of  the  yellow  chromate,  when 
half  the  |>otash  is  removed,  and  the  bichromate  crystallizes 
by  slow  evaporation  in  brilliant  red  crystals  of  a  rhombic  form, 
which  are  soluble  in  ten  parts  of  cold  water. 

595.  Chromate  of  Lead — Chrome  Yellow— (PbO,CrO3,) 
is   the    well-known    pigment    prepared  by    precipitating  the 
nitrate  or  acetate  of  lead  by  a  solution  of  chromate  or  bichro- 
mate of  potash.     Chrome  Green  is  the  oxyd  of  chrome,  pre- 
pared in  a  particular  way. 

Chlorochromic  Acid  (CrO^Cl)  is  a  deep  red  volatile 
liquid  resembling  bromine,  which  appears  when  equal 
weights  of  common  salt  and  bichromate  of  potash  are 
intimately  mixed,  and  heated  in  a  retort  with  three  parts  of 
sulphuric  acid.  The  chlorochromic  acid  distils  over,  filling 
the  receiver  with  a  superb  ruby-red  vapor.  Water  decom- 
poses it,  forming  chromic  and  hydrochloric  acids. 

33.    NICKEL. 

Equivalent,  29*59.     Symbol,  Ni. 

596.  Nickel  is  rather  a  rare  metal,  but  may  be  prepared 
from  the  speiss  or  crude   nickel  of  commerce.     It  is  white 
and   malleable,  having  a   density  of  8'27,  and   fuses  above 
3000°.     It  is  not  easily  oxydized,  and   is  one  of  the  two  or 


Describe  the  chlorids  of  chromium.  ,"594.  How  is  chromate  of 
potash  formed  T  Bichromate  of  potash  is  how  formed  ?  595.  What 
is  chrome  yellow  ?  What  chrome  green  ?  Describe  chlorochromic 
acid.  596.  In  what  state  does  nickel  occur  in  nature  ? 


COBALT.  321 

three  magnetic  metals  ;  magnets  may  be  made  of  it  nearly 
as  powerful  as  those  of  iron.  Nickel  is  almost  always  found 
alloyed  in  masses  of  meteoric  iron.  In  this  country  it  has 
been  obtained  at  Chatham,  Ct.  as  an  arseniuret,  and  also  at 
Mine  la  Motte,  in  Missouri,  as  an  earthy  oxyd  associated 
with  cobalt.  A  beautiful  green  hydrous  oxyd  of  nickel  has 
been  found  lately  in  Lancaster  Co.,  Pa.,  having  the  composi- 
tion NiO  +  2HO. 

There  are  two  oxyds  of  nickel.  The  protoxyd  (NiO)  is 
prepared  by  precipitating  a  solution  of  nickel  by  caustic  pot- 
ash, which  gives  a  grass-green  hydrated  oxyd,  which  by 
heat  loses  its  water  and  becomes  gray.  The  oxyd  of  nickel 
is  isomorphous  with  magnesia,  and  has  been  obtained  crys- 
tallized in  regular  octahedrons.  The  salts  of  this  oxyd  have 
a  fine  green  color,  which  they  impart  to  their  solutions. 

The  peroxyd  of  nickel  (NiO3)  is  a  dull  black  powder,  of 
no  particular  interest. 

597.  The  Sulphate  of  Nickel  (NiO,SO3  +  7HO)  is  a  fine- 
ly crystallized  salt  occurring  in  green  prisms,  which  lose  their 
water   of  crystallization  by  heat.     It    forms  beautiful  well 
crystallized  double   salts,  with  the  sulphates  of  potash  and 
ammonia.     Oxalic  acid   precipitates   an  insoluble  oxalate  of 
nickel   from  the  solution  of  the  sulphate,  and   the  metallic 
nickel  is  easily  obtained  from  the  oxalate  by  heat. 

Nickel  is  chiefly  employed  in  making  German  silver,  a 
white  malleable  alloy,  composed  of  copper  100,  zinc  60,  and 
nickel  40  parts. 

34.    COBALT. 

Equivalent,  29-52.     Symbol,  Co. 

598.  Cobalt   is   a   metal   almost  always  associated  with 
nickel,  and  closely  resembling  it  in   many  of  its   reactions. 
When  pure  it  is  a  brittle  reddish  white  metal,  with  a  density 
of  8'53,  and  melts  only  at  very  high  temperatures.     It   is 
generally  said  to  be  magnetic,  but  is  not  so  when  quite  pure. 
It  dissolves  with  difficulty  in  strong  sulphuric  acid,  and  is  not 
oxydized  in  air.     It  forms  two  oxyds  every  way  analogous 
to  those  of  nickel.     Its  protoxyd  is   a  grayish  pink  powder, 
very  soluble  in  hydrochloric  acid,  and  forming   pink  salts. 
This  oxyd  occurs  native. 

Describe  its  properties.  What  are  its  oxyds  ?  In  what  form  does 
the  protoxyd  crystallize  ?  597.  Describe  the  sulphate  and  oxalate 
of  nickel.  What  is  the  composition  of  German  silver  ?  598.  Wha* 
are  the  characters  of  cobalt  ? 


322  METALLIC    ELEMENTS. 

The  Chlorid  of  Cobalt  (CoCl)  is  formed  by  dissolving  the 
oxyd  in  hydrochloric  acid.  The  solution  is  pink,  and  when 
verv  dilute  may  be  used  as  a  blue  sympathetic  ink,  which 
may  be  made  green  by  mixing  a  little  chlorid  of  nickel. 
Writing  made  with  this  on  paper  is  colorless  when  cold,  but 
becomes  of  a  fine  blue  or  green  when  gently  warmed,  and 
loses  its  color  again  on  cooling. 

The  salts  of  cobalt  and  nickel  are  isomorphous  with  those 
of  magnesia.  They  are  not  thrown  down  by  sulphureted 
hydrogen,  but  give  blue  or  green  precipitates  with  potash, 
soda,  and  their  carbonates.  The  same  precipitates  with 
ammonia  are  soluble  in  excess  of  that  reagent.  Oxyd  of 
cobalt  imparts  a  splendid  blue  to  glass,  and  the  pulverized 
glass  of  this  color  is  called  smalt  and  powder  blue.  Zajfre 
is  an  impure  oxyd  of  cobalt  used  to  give  the  fine  blue  color 
to  common  earthen  ware. 

35.  ZINC. 

fyuivalent,  33.     Symbol,  Zn.     Density,  6-86. 

599.  Zinc  is  an  important  and  rather  common  metal.     It 
is  not  found  native,  but  a  peculiar  red  oxyd  of  zinc  abounds 
at  Sterling,  Xesv    Jersey,    and    calamine    or    carbonate    of 
zinc  is  found  abundantly  in  many  places.     The  ores  of  zinc 
are  reduced  by  heat  and   charcoal,  in   large  crucibles  closed 
at  top,  but  having  an  iron  tube  descending  from  near  the  top, 
through  the  bottom,  and  terminating  in  a  vessel   of  water. 
The  metal  being  volatile,  rises  and   escapes   by  the  tube  into 
the  water.     This  is  called  distillation  by  descent. 

600.  Zinc  is  a  bluish  white   metal,  easily  oxydized  in  the 
air,  and    crystallizes    in    broad    foliated    laminae,  well   seen 
in  the  fracture  of  an  ingot  of  the  commercial  article.     It  is 
called  spelter  in  the  arts,  and  is  used  chiefly  to  alloy  copper 
in  forming  brass.     Zinc  is  not  a  malleable  metal,  at  ordinary 
temperatures,  but  at  a  temperature  of  between  250°  and  300° 
it    becomes    quite    malleable,  and    is  then  rolled  into  sheet 
zinc.     At  400°  it  is  again  quite  brittle,  and  may  be  granula- 


What  interesting  experiment  is  mentioned  with  the  chlorid  ? 
With  what  metal  is  the  oxyd  of  cobalt  and  its  salts  isomorphous  ? 
What  use  is  made  of  the  oxyd  of  cobalt  ?  599.  How  is  zinc  reduced 
from  its  ores  ?  600.  What  are  its  properties  ?  At  what  temperature 
is  it  malleable  ? 


CADMIUM.  323 

ted  by  blows  of  the  hammer ;  at  773°  it  melts,  and  if  air 
has  access  to  it,  it  takes  fire,  and  burns  rapidly  with  a  bril- 
liant whitish  green  flame,  giving  off  flakes  of  white  oxyd  of 
zinc,  sometimes  called  lana  philosophica.  It  is  completely 
volatile  at  a  red  heat. 

The  Chlorid  of  Zinc,  ZnCl,  is  a  salt  easily  prepared  when 
zinc  is  dissolved  in  hydrochloric  acid,  hydrogen  being 
evolved. 

Sulphuret  of  Zinc,  Blende,  ZnS,  occurs  native  in  the 
forms  of  the  first  crystallographic  class,  and  is  colored  yel- 
low, brown,  and  black.  This  is  one  of  the  ores  of  zinc 
(called  black  Jack)  from  which  the  metal  is  obtained. 

The  oxyd  (ZnO)  is  a  white  powder,  insoluble  in  water, 
but  easily  dissolved  in  all  acids,  forming  a  series  of  salts,  of 
which  the  most  important  is — 

Sulphate  of  Zinc,  or  White  Vitriol,  ZnO,  SO3-f  7HO.— - 
This  salt  has  the  same  form  as  the  sulphate  of  magnesia,  and 
looks  extremely  like  it.  It  dissolves  in  2^  parts  of  cold 
water,  and  forms  double  salts  with  the  sulphates  of  ammo- 
nia and  potash.  It  is  a  powerful  emetic. 

Sulphuret  of  ammonium  throws  down  a  characteristic 
white  precipitate  of  sulphuret  of  zinc  from  its  neutral  solu- 
tions. 

36.    CADMIUM. 

Equivalent,  55'74.     Symbol,  Cd.     Density,  8'65. 

601.  Cadmium  is  generally  found  associated  with  zinc, 
and  is  almost  as  volatile  as  mercury.  It  is  quite  malleable, 
white,  and  harder  than  tin.  It  fuses  at  442°,  and  volatilizes 
at  a  temperature  a  little  above  this.  It  is  not  easily  oxydiz- 
ed,  and  is  but  slightly  soluble  in  hydrochloric  or  sulphuric 
acids.  Nitric  acid  dissolves  it  with  ease,  forming  a  salt 
from  which  sulphureted  hydrogen  throws  down  a  very  char- 
acteristic orange-yellow  sulphuret.  This  compound  is  also 
found  native  and  crystallized,  (greenockite.) 

Its  oxyd  (CdO)  is  a  bronze  powder,  formed  by  igniting  the 
nitrate  or  carbonate. 


Is  it  combustible  ?     Describe  the  sulphuret.     What  is  said  of  the 
sulphate  ?     601.  What  are  the  properties  of  cadmium  ?     Describe 

its  sulphuret. 


324  METALLIC  ELEMENTS. 


37.  LEAD. 

Equivalent,  103-56.     Symbol,  Pb.     Density,  11-35. 

602.  This  useful  and  familiar  metal  occurs  in  boundless 
profusion   in  this  country,  chiefly  as  galena,  or  sulphuret  of 
lead,  from  which  the  metal  is  easily  obtained  by  smelting  the 
ore  with  a  limited   amount  of  fuel,  at  a  low  heat.     The  car- 
bonate, phosphate,  chromate,  and  arscniate,  are  also  natural 
salts  of  lead   much  prized   by  the  mineralogist.     Lead  is  a 
bluish  gray  metal,  very  soft  and  ductile,  but  not  very  tena- 
cious;  it  oxydizes  in  the  air  quite  rapidly,  forming  a  coat  of 
oxyd,  or  carbonate,  which  protects  it  from  further  corrosion. 
Its  density  is   11-35,  and   it   fuses  at  612°;  when  melted  it 
combines  rapidly  with  oxygen  from  the  air,  forming  either 
protoxyd,  or  red  oxyd,  according  to  the  heat. 

Lead  is  slowly  acted  upon  by  soft  or  rain  water,  and  in 
some  cases  by  hard  water ;  so  that  it  is  unsafe  to  use  water- 
pipes  of  lead,  unless  it  has  been  proved  by  experiment  that 
the  particular  water  in  question .  does  not  act  on  this  metal. 
It  is  a  deadly  poison,  at  least  in  the  form  of  carbonate,  which 
is  generally  produced  under  these  circumstances. 

Lead  does  not  easily  dissolve  in  dilute  acids,  except  in 
nitric,  with  which  it  forms  a  soluble  salt :  strong  sulphuric 
acid  dissolves  it  when  heated,  forming  a  nearly  insoluble 
sulphate  of  lead. 

There  are  three  oxyds  of  lead,  of  which  only  the  protoxyd 
has  basic  properties. 

603.  Protoxyd  of  Lead  ;  Litharge,  PbO. — This  oxyd  is 
a  yellow   powder,   formed   by  slowly  oxydizing   lead,  with 
heat.     It   is   slightly   soluble   in  water,  and  the  solution    is 
alkaline.     It  fuses  easily,  and  then  dissolves  silica  with  great 
rapidity;  hence  its  use  in  glazing  pottery,  (571,)  and  in  the 
manufacture  of  glass,   (535.)      It   forms   a   large  class  of 
definite  salts,  which   have  often  a  sweet  taste,  as  is  seen  in 
the   acetate    or    sugar   of  lead.      The   sesqnioxyd   has   the 
formula  PbaOa,  and  is  a  reddish  yellow  insoluble  powder. 

The  Pcroxyd,  PbO2,  is  prepared  by  acting  on  the  red  lead 


602.  What  is  the  chief  ore  of  lead  ?  Describe  the  metal.  How 
does  water  affect  lead  ?  603.  Describe  the  protoxyd  of  lead.  The 
other  oxyds.  What  use  is  made  of  litharge  ? 


LEAD.  325 


with  nitric  acid  ;  it  is  a  puce-colored   body  which  acts  the 
part  of  an  acid,  withi bases  forming  salts. 

604.  Red   Oxy£or  Red  Lead,  Pb3O4.— This  is  a  com- 
mon  pigment,  ancHs  formed  when  melted   lead  is  exposed  to 
a  temperature  of  600°  or  700°.    It  is  of  variable  constitution, 
according  to  the  temperature  at  which  it  is  prepared.     Acted 
on   by  hydrochloric  acid,  it  evolves  chlorine,  and  with   sul- 
phuric acid,  oxygen  is  given  off.     It  is  preferred  to  litharge 
for  glass  making. 

The  chlorid  and  iodid  of  lead  possess  no  particular  interest  ; 
the  latter  crystallizes  in  beautiful  yellow  scales  from  its  so- 
lution in  hot  water.  The  sulphuret  of  lead  is  the  native 
galena  already  mentioned,  and  occurs  in  brilliant  cleavable 
cubes.  Sulphureted  hydrogen  throws  down  a  black  sulphu- 
ret from  all  soluble  salts  of  lead,  being  the  best  test  of  its 
presence. 

605.  Zinc  precipitates  it  from  its  solutions  by  electrical 
action   (248)   in    beautiful   crystalline   plates  of 

metallic  lead,  which  assume  a  branching  form, 
often  an  inch  or  two  in  length,  and  hence  called 
the  lead  tree,  or  arbor  saturni,  from  the  alche- 
rnistic  name  of  this  metal.  The  acetate  or  nitrate 
may  be  employed  ;  an  ounce  of  the  salt  is  dis- 
solved in  two  quarts  of  water,  and  a  piece  of 
clean  zinc  suspended  in  it  by  a  thread  ;  the  pre- 
cipitation is  gradual,  and  occupies  one  or  two 
days.  The  arrangement  is  seen  in  the  annexed 
figure. 

606.  Carbonate  of  Lead ;    White  Lead ;    PbO,CO2.— 
This  salt  is   found   beautifully  crystallized  in   nature,  but  is 
prepared  artificially  in  very  large  quantities,  for  the  purposes 
of  a  paint.     This  pigment  is  obtained  by  casting  lead  in  very 
thin  sheets,  which  are  then  rolled  up  into  a  loose  scroll  and 
placed   in  a  pot  over  a  small   quantity  of  vinegar,  and  so 
arranged  as  not  to  project   above  the  pot,   nor  touch    the 
vinegar.      Many  thousands  of  these  pots  are  arranged  in 
successive  layers  over  each  other,  with  boards  between,  and 
the  interstices  filled   with    spent  tan,  or  fermenting  stable 
dung,  which  gives  a  gentle  heat  to  the  acid.     After  a  time 
the  lead  is  completely  converted  into  an  opake  white  crust 


605.  How  is  metallic  lead  produced  from  its  solution  ?    606.  How 
is  the  carbonate  prepared,  and  for  what  is  it  used  ? 

28 


326  METALLIC    ELEMENTS. 


of  carbonate.  The  theory  of  this  process  will  be  explained 
when  we  describe  the  acetates  of  leadJjj|prganic  chemistry.) 
White  lead  is  now  largely  adulterated  bjLulphate  of  baryta, 
but  the  fraud  may  be  easily  detected  b^iissolving  the  car- 
bonate in  an  acid,  when  the  sulphate  of  baryta  will  be  left 
behind.  Carbonate  of  lead  is  highly  poisonous. 

38.    URANIUM. 

607.  This  is  a  very  rare  substance,  found  only  in  pitch- 
blende, uranite,  and  a  few  other  rare  minerals.     Its  chemical 
history   is,    however,    possessed   of    considerable    interest. 
There  are  three   oxyds   of  uranium,  viz.,  UO2,  U203,  and 
U4O6.     The  metal  is  usually  obtained  as  a  dark  powder, 
but  can  be  condensed  into  a  white  malleable  form.     It  forms 
beautiful  yellow  salts.     The  phosphate  of  uranium  and  cop- 
per (uranite)  is  one  of  the  most  beautiful  of  minerals. 

39.  COPPER. 
Equivalent,  31-65.     Symbol,  Cu.     Density,  8-895. 

608.  Copper  has  been  in  familiar  use  since  the  times  of 
Tubal  Cain,  and  is  one  of  the  most  important  metals  to  the 
wants   of  society.     It   is   often  found  in  the  metallic  state. 
The  metallic  copper  of  Lake  Superior  is  associated  with  na- 
tive silver,  and  small  proportions  of  silver  are  also  often  alloy- 
ed with  the  copper.     One    mass  from   this   region  now  at 
Washington,  weighs  over  3000  pounds.     Its  most  usual  ores 
are  the  red  oxyd  of  copper  and  the  copper  pyrites,  or  sul- 
phuret  of  copper  and  iron.     The  blue  and  green  malachites, 
or  carbonates  of  copper,  and  several  other  salts  of  this  metal, 
are   also    found    in  the  mineral  kingdom.     Copper  is  very 
malleable,  and   is  the  only  red  metal  except  titanium.     It 
fuses  at  1996°,  and  has  a  density  of  8-895,  which  may  be  in- 
creased to  8-95  by  hammering.     It   does  not  change  in  dry 
air,  but  in  moist  air  becomes   covered  with  a  green  coat  of 
carbonate.      It  is   stiffened   by  hammering   or   rolling,  and 
softened  again  by  heating  and  quenching  in  water.     It  may 
be  drawn  into  very  fine  wire,  which  is  an  excellent  conduc- 
tor of  heat  and  electricity,  and  is  much  used  in  electro-mag- 
netism, and  for  the  telegraphic  conductors. 

Nitric  acid  is  the  proper  solvent  of  copper,  sulphuric  and 

G07.  What  is  said  of  uranium?     608.  In  what  state  <loes  copper 
occur  in  nature  ?     Describe  its  properties. 


COPPER.  327 

hydrochloric  acids   scarcely  acting  upon  it.     It  forms  two 
oxyds,  the  protoxyd  and  the  suboxyd. 

609.  The  first,  or  Black  Oxyd  of  copper,  CuO,  is  the 
base  of  all  the  blue  and  green  salts  of  copper.     It  is  formed 
by  decomposing  the  nitrate  with  heat.     It  is  black  and  very 
dense,  quite  soluble  in  acids,  and  forms  many  important  salts 
which  are  isomorphous  with  those  of  magnesia.     It  yields 
ail  its  oxygen  to  organic  matters  at  a  red  heat,  and  for  this 
purpose  is  much  used  in  their  analysis. 

The  Suboxyd  or  Red  Oxyd  of  Copper,  Cu2  O,  is  found  na- 
tive in  beautiful  octahedral  crystals,  and  is  also  formed  when 
copper  is  oxydized  by  heat.  This  oxyd  communicates  to  glass 
a  magnificent  ruby-red  color.  The  chlorids  and  iodids  of 
copper  are  of  no  great  importance. 

610.  Sulphate  of  Copper  ;  Blue  Vitriol,  CuO  SOg+ 5HO, 
is   an   important   salt,  crystallizing  in   large  beautiful  blue 
rhombs,  which  are  soluble  in  four  parts  of  cold  and  two  parts 
of  hot  water.     It  loses  its  water  by  a  gentle  heat  and  falls  to 
a  white  powder.     It  is  much  used  in   dyeing,  and  for  excit- 
ing galvanic  batteries.     With  ammonia  it  forms  a  dark  blue 
crystallizable  compound. 

611.  Nitrate  of  Copper,  CuO,  NO5  +  3HO,  is  formed  by 
dissolving  copper  in   nitric  acid  to  saturation,  and  is  a  deep 
blue  crystallizable,  deliquescent  salt,  very  corrosive,  and  easily 
decomposed  ;   a  paper  moistened  with  a  strong  solution  of 
this  salt  cannot  be  rapidly  dried  without  taking  fire,  from  the 
decomposition  of  nitric  acid. 

Ammonia  detects  the  smallest  traces  of  this  metal  in 
solution,  by  the  deep  violet  blue  of  the  ammoniacal  salt  of 
copper  which  is  formed.  Iron  precipitates  it  from  its  acid 
solutions  as  a  brilliant  red  coating. 

CLASS  V.    METALS  WHOSE  OXYDS  ARE  WEAK  BASES 
OR  ACIDS. 

40.    VANADIUM.         41.    TUNGSTEN.         42.    MOLYBDENUM. 
43.    COLUMBIUM.  44.    TITANIUM. 

612.  The  first  five  metals  of  this  class  are  so  rare  that 
we  shall  dwell  on  them  very  briefly. 

609.  What  are  the  most  important  facts  relative  to  the  black  oxyd 
of  copper  ?  Describe  the  suboxyd.  610.  Describe  sulphate  of 
copper.  611.  What  is  the  nitrate?  How  does  it  affect  organic 
matter  ?  How  is  copper  detected  ?  612.  Enumerate  the  five  metals 
described  in  this  section. 


328  METALLIC    ELEMENTS. 

(40.)  Vanadium  is  described  as  a  very  infusible,  brittle, 
white  metal,  and  dissolved  only  by  aqua  regia,  affording  a 
blue  solution.  It  is  found  only  in  one  or  two  very  rare 
minerals,  as  in  the  vanadinite,  or  vanadiate  of  lead,  acting 
the  part  of  an  acid.  It  appears  to  be  closely  allied  to  chro- 
mium. 

(41.)  Tungsten,  so  named  in  allusion  to  its  great  weight,  is 
found  as  tungstic  acid  in  two  or  three  rare  minerals,  viz. 
wolfram  and  tungstate  of  lime.  The  native  tungstic  acid  has 
also  been  observed  at  Monroe,  Ct.  Metallic  tungsten  re- 
semftles  vanadium  in  physical  characters,  but  it  takes  fire 
when  heated  in  air  in  a  state  of  division.  It  has  a  density 
of  17-4. 

There  are  two  oxyds  of  tungsten :  the  first  (W02)  forms 
no  salts  ;  the  second,  tungstic  acid,  (WO3,)  is  a  yellow 
powder,  insoluble  in  water,  but  is  easily  dissolved  in 
ammonia. 

(42.)  Molybdenum. — Sulphuret  of  molybdenum  is  a  rather 
common  mineral,  found  in  soft  scales  resembling  graphite. 
The  metal  is  obtained  from  its  oxyd,  and  is  very  infusible, 
white  and  brittle,  having  a  density  of  8-6. 

It  forms  three  oxyds,  MO,  MO2,  MO3,  of  which  the  last 
only  has  much  importance ;  it  resembles  tungstic  acid  in 
being  soluble  in  alkalies.  It  forms  a  beautiful  yellow  salt 
with  lead,  which  is  found  native.  The  native  sulphuret  may 
be  converted  into  impure  molybdic  acid  by  heat. 

(43.)  Columbium,  or  Tantalum. — This  metal  was  named 
after  this  country  by  Mr.  Hatchett,  its  discoverer,  who  found 
it  among  some  ores  sent  to  the  Royal  Society  in  London,  by 
Gov.  Winthrop,  from  Connecticut. 

Columbite  (columbate  of  iron)  is  found  at  Haddam  and 
Middletown,  sometimes  in  large  crystals.  Professor  Shepard 
procured  the  metal  in  a  crucible  lined  with  charcoal,  as  a 
dull,  very  infusible,  brittle  body,  having  a  density  of  5-7. 
Columbium  forms  two  oxyds,  TO2  and  TO3.  The  last  is 
columbic  acid,  a  white  powder,  soluble  in  acids,  and  forms 
almost  insoluble  salts  with  the  alkalies  and  metallic  oxyds. 
It  is  with  this  acid  that  the  oxyds  of  the  two  new  metals, 
pelopium  and  niobium,  are  associated. 

(40.)  What  is  vanadium  ?  Describe  tungsten.  (41.)  What  oxyds 
of  tungsten  are  named  ?  (42.)  How  is  molybdenum  found  ?  What 
oxyd  and  what  native  salt  of  it  are  named  ?  (43.)  Give  the  history 
of  columbium.  In  what  mineral  is  it  found  ?  Describe  its  oxyds. 


TIN.  •  329 

44.  Titanium. — This  metal  is  found  crystallized  in  small 
brilliant  cubes  of  a  copper-red  color  in  the  slags  of  some  iron 
furnaces.  Its  oxyd,  beautifully  crystallized,  is  well  known 
to  mineralogists,  as  rutile,  anatase,  and  Brookite,  three 
minerals  specifically  distinct,  but  chemically  identical. 
Titaniferous  iron  ore  is  also  an  abundant  mineral. 

Titanic  Acid,  TiO2,  is  soluble  in  strong  hydrochloric  acid, 
but  on  dilution  and  boiling  is  all  precipitated.  It  is  a  white 
insoluble  powder,  much  resembling  silica.  It  gives  a  peculiar 
tint  to  porcelain,  and  is  used  for  this  purpose  in  preparing 
artificial  teeth. 

45.   TIN. 

Equivalent,  58-82.    Symbol,  Sn,  (Stannum.)    Density,  7-29. 

613.  Tin  is  one  of  those  metals  which  have  been  known 
from  the   most  remote  antiquity.     The  mines  of  Cornwall 
have  been  worked  for  the  oxyd  of  tin,  since  the  times  of  the 
Greeks  and  Phoenicians.     It  has  been  found  in  this  country 
only  at  Jackson,  N.  H.,  in  small  quantities.     Tin  is  a  white 
metal  with  a  brilliant  lustre,  not  easily  tarnished,  and  resist- 
ing the  action  of  acids  to  a  remarkable  degree.     It  is  soft, 
very  ductile,  laminable,  and  malleable.      Tinfoil  is  made  of 
one-thousandth  of  an  inch  in  thickness,  or  even  much  thinner. 
A  bar  of  tin  when  bent  gives  a  peculiar  crackling  sound,  from 
the  disturbance  of  its  crystalline  structure,  familiarly  called 
the  cry  of  tin.     It  is  one  of  the  best  conductors  of  heat  and 
electricity. 

614.  Tin  has  a  density  of  7-29,  and  fuses  at  442°.     Its 
alloys  are  veryvaluble;  gun-metal   (copper  90,  tin  10)  is 
one  of  the  strongest  alloys  known,  of  a  reddish  yellow  ;  bell- 
metal  (copper  78,  tin  22)  is  a  very  sonorous  and  brittle  alloy, 
of  a  pale  yellow ;  and  speculum  metal  (copper  70  to  75,  and 
tin   25  to  30)  is  a  brilliant,  almost  white,  and  excessively 
brittle  alloy.     Pewter  is  a  mixture  of  tin  and   antimony  or 
lead.      Tin-plate  is  only  sheet-iron  coated  with  tin. 


(44.)  How  is  titanium  found  ?  What  minerals  contain  it  ? 
Describe  titanic  acid.  613.  What  history  is  given  of  tin  ?  What 
are  its  equivalent  and  general  properties  ?  614.  Give  its  density  and 
fusibility.  What  is  said  of  its  alloys  with  copper  ?  What  is  tin- 
plate  ?  and  what  pewter  ? 

28* 


330  METALLIC    ELEMENTS. 

Strong  nitric  acid  does  not  dissolve  tin,  but  the  addition  of 
a  little  water  to  the  acid  causes  a  violent  action,  and  the  tin 
is  speedily  oxydized. 

615.  There  are  three  oxyds  of  tin:  the   protoxyd,  SnO ; 
the  sesquiuxyd,  Sn2O3 ;  and   the  peroxyd,  SnO2.     (I.)  This 
is  obtained   by  precipitating  a  solution  of  protochlorid  of  tin 
with  an  alkaline  carbonate,  which   yields  a  bulky  hydrate  of 
the  protoxyd.     It  is  a  very  unstable  compound,  passing  into 
the  |>eroxyd  at  a  very  moderate  heat.     (2.)    The  scsquioxyd 
is  a  grayish   powder,  which    has   been   but   little  examined. 
(3.)  The  peroxyd  is  found  native  in  the  beautiful  crystallized 
tin  stone.     It  may  be  obtained  in  a  soluble,  and  an  insoluble 
condition.     When  the  pcrchlorid  is  precipitated  by  an  alkali, 
the    bulky    white    precipitate    of    hydrated    peroxyd    which 
appears,  is  easily  soluble  in  acids  ;  but  if  tin  is  acted  on   by 
an  excess  of  moderately  strong  nitric  acid,  a  white  insoluble 
powder  is  formed,  which  is   not  acted   on   by  the  strongest 
acids.      Heat  converts    both    into  a    lemon-yellow   powder, 
which  dissolves   in  alkalies,  but   not   in  acids,  and  which  is 
known   as   stannic  acid ;  it  reddens   test-paper,  and    forms 
salts.     The  putty  used  to    polish    stone  and    glass    is   the 
peroxyd  of  tin. 

616.  Protochlorid  of  Tm,  which  is  prepared  by  dissolving 
tin  in  hot  hydrochloric  acid,  is  a  powerful  deoxydizing  agent, 
and  reduces  the  salts  of  silver,  mercury,  platinum,  &c.,  to 
the  metallic  state.     The  anhydrous   protochlorid   is  formed 
by  heating  protochlorid  of  mercury  with  powdered  tin. 

617.  Perchlorid  of  Tin  is  a  dense  fuming   liquid,   long 
known  as  the  fuming  liquor  of  Labavius.     It  is  formed  by 
distilling  a  mixture  of  1    part  of  powdered   tin  and  5  of 
corrosive  sublimate.     The  tin  mordant  used  by  the  dyers  is 
formed  by  dissolving  tin   in   hydrochloric  acid,  with  a  little 
nitric,   at  a  low   temperature,   or  by   passing  chlorine  gas 
through  the  protochlorid. 

The  sulphurets  of  tin  correspond  to  the  chlorids.  The 
bisulphuret  (aurum  musivum)  is  used  as  a  bronze  color  for 
imitating  gold  in  ornamental  painting  and  printing. 

How  does  strong  nitric  acid  affect  it  ?  615.  What  oxyds  of  tin 
are  there  ?  What  is  the  protoxyd  ?  Describe  the  peroxyd.  What 
two  modifications  of  it  are  named  ?  How  does  heat  affect  them  ? 
What  is  «  putty  ?»  616.  How  is  protochlorid  of  tin  employed  as  a 
reagent  ?  617.  What  is  perchlorid  of  tin,  and  how  prepared  ?  What 
is  the  tin  mordant  ?  What  sulphurets  of  tin  are  there  ? 


BISMUTH.  331 

The  alchemistic  name  for  this  metal  was  Jove,  and  the 
preparations  of  tin  are  still  called  Jovial  preparations. 

46.    BISMUTH. 

Equivalent,  70-95.     Symbol,  Bi.     Density,  9-82. 

618.  Bismuth  is   found  native,  and  also   in   combination 
with  other  substances.     Native  bismuth  is   found  at  Monroe, 
Conn.      It  is  a  brittle,  highly  crystalline  metal,  of  a  red- 
dish white  color,  with  a  density  of  9-82,  and  fuses  at  497°. 
It  is  obtained  in  large  and  beautiful  cubical  crystals,  by  per- 
forating the  crust  of  a  mass  which  is  just  cooling  from  a  state 
of  fusion  in  a  crucible,  and  pouring  out  the  still  fluid  interior. 
The  vessel  will  be  lined  with  a  multitude  of  brilliant  crystals. 

It  dissolves  in  nitric  acid,  but  like  other  metals  of  this 
class,  does  not  decompose  water  under  any  circumstances. 

619.  Two  oxyds  of  bismuth  are  known.     The  protoxyd 
(BiO)  is  formed   by  gently  igniting  the  subnitrate,  and   is  a 
yellowish   powder,  easily  soluble  in  acids,  and  is  the  base  of 
all  the  salts  of  bismuth.     It  is,  however,  a  very  feeble  base, 
since  even  water  decomposes  its  salts.     The  peroxyd  (Bi2O3) 
is  not  of  much  interest. 

620.  The  Nitrate  of  Bismuth  (BiO,NO5-f  3HO)  is  the 
most  interesting  of  its  salts.     It  may   be  obtained  from  a 
strong   solution   in   large    transparent   crystals,    which   are 
decomposed    by    water.      It    is   a    striking   and    instructive 
experiment,  to  turn  the  solution  of  the  nitrate  of  bismuth  into 
a  large  quantity  of  water,  when  it  is  immediately  decomposed, 
with  the  production  of  a  copious  white  precipitate  of  subnitrate 
of  bismuth.     This  is  owing  to  the  superior  basic  power  of 
the  water,  which  takes  a  part  of  the  nitric  acid.     The  white 
precipitate  is  a  basic  nitrate,  (BiO,NO5-f  3BiO,HO.) 

621.  The  alloy  of  bismuth   known   as   Newton's   fusible 
metal,  is  formed  of  8  parts  bismuth,  5  parts  lead,  and  3  parts 
tin,  and  melts  below  212°.     It  is  much  used  in  taking  casts 
of  medals.     The  expansion  of  bismuth  in  cooling,  renders  it 
a  valuable  constituent  of  alloys,  where  sharpness  of  impression 
in  casting  is  important. 

618.  What  is  the  color  and  fusibility  of  bismuth  ?  Describe  its 
crystals,  and  the  mode  of  obtaining  them.  619.  How  many  oxyds 
has  this  metal  ?  620.  What  is  the  most  interesting  property  of  the 
nitrate  ?  621.  What  is  the  composition  of  Newton's  fusible  metal  ? 


332  METALLIC    ELEMENTS. 


47.    ANTIMONY. 

Equivalent,  129-04.    Symbol,  Sb,  (Stibium.)    Density,  6-7. 

622.  This  metal  is  derived  chiefly   from   its  native  sul- 
phuret,  which  is  a  rather  abundant   mineral.     The  metal  is 
obtained  by   fusing   the  sulphuret  with   iron-filings,  or  car- 
bonate of  potash,  which  combines  with  the  sulphur  and  sets 
free  the  metal.     It  is  a  white  brilliant  metal  with  a  blue  tint, 
forming  broad  rhomboidal  crystalline  plates.     It  is  very  brit- 
tle, and  like  bismuth  may  be  reduced   to  a   fine  powder.     It 
fuses  at  about  1000°,  or  low  redness,  and  at  a  higher  heat 
is  volatilized.     It  dissolves  in  hot  hydrochloric  acid,  but  nitric 
acid  converts  it  into  the  insoluble  white  antimonic  acid. 

Its  alloy  with  lead  is  type-metal,  which,  like  the  alloys 
of  bismuth,  gives  very  sharp  casts,  by  reason  of  the  expan- 
sion from  crystallization,  it  suffers  in  solidifying,  although  it 
is  remarkable  that  both  of  the  constituent  metals  shrink  when 
cast  separately.  Finely  powdered  antimony  is  inflamed  in 
chlorine  gas,  forming  the  perchlorid. 

623.  Three   compounds   of-    antimony   and   oxygen    are 
known,  viz : 

(1.)  Oxyd  of  Antimony,  SbO3. — This  oxyd  may  be  ob- 
tained by  digesting  the  precipitate  from  chlorid  of  antimony 
by  water,  with  carbonate  of  potash  or  soda,  or  by  burning 
antimony  in  a  red-hot  crucible.  It  is  n  fawn-colored  insol- 
uble powder,  anhydrous,  and  volatile  when  highly  heated  in  a 
close  vessel.  Boiled  with  cream  of  tartar,  (acid  tartrate  of 
potash,)  it  forms  the  well-known  tartar  emetic,  which  may 
be  obtained  in  crystals  from  the  solution. 

The  Glass  of  Antimony  is  an  impure  fused  oxyd,  prepared 
for  the  purpose  of  making  tartar  emetic.  Heated  in  air,  this 
oxyd  gains  another  equivalent  of  oxygen,  and  forms — 

624.  (2.)  Antimonious  Acid,  SbO4. — This  is  a  gray  pow- 
der, not  volatile,  insoluble  in  acids,  unless  recently  precip- 
itated.     Its    hydrate   reddens    litmus    paper,  and    combines 
with  alkalies. 

(3.)  Antimonic  Acid,  SbO5,  is  formed  as  already  stated, 


622.  How  is  antimony  obtained  ?  What  are  its  properties  ?  623. 
How  many  compounds  does  antimony  form  with  oxygen  ?  624.  De- 
scribe the  two  acids  of  antimony. 


ANTIMONY.  333 

when  antimony  is  digested  in  an  excess  of  strong  nitric  acid. 
It  dissolves  in  alkalies,  with  which  it  forms  definite  salts, 
that  are  again  decomposed  by  acids,  hydrate  of  antimonic 
acid  being  thrown  down.  The  hydrate  loses  its  water  be- 
low a  red  heat,  becoming  a  crystalline  fawn-colored  powder, 
and  by  a  higher  heat  one  equivalent  of  oxygen  is  expelled, 
antimonious  acid  being  formed. 

625.  There  are  chlorids  and  sulpkurets  of  antimony,  cor- 
responding to  the  oxyd  and  to  antimonic  acid. 

The  Terchlorid,  Butter  of  Antimony,  SbCl3,  is  made  by 
distilling  the  residue  of  the  solution  of  sulphuret  of  antimony 
in  strong  hydrochloric  acid.  When  a  drop  of  the  distilled 
liquid  forms  a  copious  white  precipitate  on  falling  into  water, 
the  receiver  is  changed,  and  the  pure  chlorid  is  collected. 
It  is  a  highly  corrosive  fuming  fluid,  and  by  cooling  forms  a 
crystalline  deliquescent  solid.  It  is  used  in  medicine  as  a 
caustic.  Water  decomposes  it,  but  it  dissolves  in  hydro- 
chloric acid  unchanged ;  water  poured  into  the  solution 
throws  down  a  bulky  precipitate  which  is  a  mixture  of  oxyd 
and  chlorid  of  antimony,  and  has  long  been  known  by  the 
name  of  powder  of  algaroth. 

The  bromid  of  antimony  is  a  crystalline  volatile  com- 
pound. 

626.  The  Ter sulphuret  of  Antimony,  SbS3,  constitutes  the 
common  commercial  sulphuret,  and  the  beautiful  crystallized 
native  mineral. 

The  Pentasulphuret  of  Antimony,  SbS5,  is  formed  by  boil- 
ing the  tersulphuret  with  potash  and  sulphur,  and  throwing 
down  the  compound  in  question  by  an  acid,  as  a  golden  yel- 
low sulphuret,  known  by  the  name  of  sulphur  auratum, 
or  golden  sulphur  of  antimony.  More  generally,  how- 
ever, the  decomposition  on  adding  an  acid,  as  above,  gives 
us  the  oxy sulphuret  of  antimony,  (SbS3  +  SbO3)  which  is 
a  characteristic  reddish-orange  precipitate.  This  is  the  sub- 
stance known  as  kermes  mineral,  and  is  an  article  of  the 
older  medical  practice.  The  solution  of  sulphuret  of  anti- 
mony in  caustic  potash  and  sulphur,  is  a  case  in  which  sul- 
phuret of  potassium  is  a  sulphur  base,  and  sulphuret  of  anti- 
mony, a  sulphur  acid. 


625.  Describe  the  terchlorid  and  its  decomposition.     626.  What 
is  said  of  the  chlorids  and  sulphurets  ?    What  is  formes  mineral? 


334  METALLIC   ELEMENTS. 

48.    ARSENIC. 

Equivalent,  75-21.     Symbol,  As.     Density,  5-884. 

627.  Metallic  Arsenic  is   found   native   in  thick  crusts, 
called   testaceous  arsenic,  evidently  deposited  by  sublimation. 
It  is  however  more  usually  obtained   from  roasting  the  ores 
of  cobalt,   nickel,   and   iron,   with  which   metals  it   is  often 
combined,   forming   arseniurels.     The   vapors  of  arsenious 
acid   given  out  in  the  roasting,  are  condensed  in  a  long  hori- 
zontal  chimney,  or  in  a  dome  constructed  for  the   purpose ; 
the   first    product    being   purified   by  a  second   sublimation. 
Arsenic  is  a  brilliant  steel-gray   metal,  brittle,  and  easily 
crystallized.     It  cannot  be  sublimed   unchanged  in   presence 
of  air,  but   may  be  so  in  close  vessels,  at  a  temperature  of 
356°,    without    previously   melting.     Its  vapor   has   a  very 
powerful   garlic-like  odor,  like   phosphorus.     This   metal   is 
known  by  druggists  under  the  absurd  name  of  cobalt,  and  is 
sold   in  powder  to  destroy   flies.     Metallic  arsenic  is  easily 
obtained  by  subliming  the  common  white  arsenic  with  black 
flux,  (489,)  in  a  vessel  of  hard  glass,  like  a  cologne  vial  or 
oil   bottle.     The   metal   forms  a  brilliant   black  crust  in  the 
upper  and  cooler  parts  of  the  vessel. 

Arsenic  forms  two  compounds  with  oxygen. 

628.  Arsenious  Acid — White  Arsenic  —  Rafs  Bane, 
AsO3. — This  well  known  and   fearful   poison  is  formed  as 
just  stated,  when  metallic  arsenic  is  sublimed  in  air,  or  when 
any  of  the  ores  of  arsenic  are  roasted.     This  acid  is  what  is 
usually    known   as    arsenic   in   commerce.      When  newly 
sublimed,  it  is  a  hard  transparent  glass,  brittle,  and  with  a 
density  of  3'7.     It  slowly  changes  to  a  white  opake  enamel. 
As  sold   in   commerce,   it    is   usually    reduced    to  a  white 
powder,  rarely   found  without   adulteration.     It  sublimes  at 
380°,   without   change,   and   crystallizes    in   brilliant   octa- 
hedrons, as  may  be  well  seen  by  heating  a  small  quantity  in 
a  glass  tube.     Its  vapor  is  inodorous,  but  if  sublimed   from 
charcoal  it  gives  the  peculiar  garlic  odor  of  metallic  arsenic, 
being  reduced  to  that  state.     It  is  soluble  in  about  10  parts 
of  hot  water,  and  is  almost  tasteless,  with  a  faint  sweetish 


627.  How  is  arsenic  obtained,  and  what  are  its  properties  ?     628 
Describe  arsenious  acid. 


ARSENIC.  335 

flavor,  which  renders  it  the  more  dangerous  poison,  since  no 
warning  is  given  to  the  victim  who  takes  it,  as  in  case  of 
most  other  metallic  poisons.  The  solution  in  water  is  acid 
to  test-paper,  and  deposits  nearly  all  its  arsenic  in  crystals, 
on  cooling.  Hydrochloric  acid  dissolves  it,  as  also  do 
alkalies,  which  however  do  not  form  crystallizable  salts 
with  it.  The  best  antidote  to  the  poisonous  effects  of  arsenic 
is  the  hydrated  peroxyd  of  iron,  freshly  precipitated,  and  used 
in  its  gelatinous  condition. 

629.  Arsenic   Acid,   As05.  —  This   acid   is    formed    by 
adding  nitric  acid  to  the  solution  of  white  arsenic,  in  hydro- 
chloric acid,  as  long  as  any  red  vapors  of  nitrous  acid  show 
themselves,  and  then  carefully  evaporating  the  solution  to 
entire  dryness ;  a  white  porous  subcrystalline.  mass  remains, 
which  is  slowly  soluble  in  water.     Its  solution  is  a  powerful 
acid,  quite  similar  in  chemical  characters  to  phosphoric  acid. 
The  analogy  is  so  great  that  there  is  a  complete  similarity  in 
constitution,  and  even  in  external  appearance,  between  all  the 
salts  of  these  two  acids.     For  every  tribasic  phosphate  we 
have  an  arseniate,  not  only  similar  in  constitution,  but  iso- 
morphous,  and  so  resembling  it  in  all  its  external  properties 
as  not  to   be  distinguished   by  the  eye.     Thus  the  tribasic 
phosphate  of  soda,  (528,)  and  the  tribasic  arseniate  of  soda, 
are — 

Phosphate  of  soda,  PO6,2NaOHO  -f  24Aq. 

Arseniate  of  soda,  AsO5,2NaOHO  -f  24 Aq. 

These,  and  many  other  facts,  lead  to  the  opinion  that  the 
elements  are  themselves  isomorphous,  and  in  fact  arsenic  has 
no  claim  to  the  metallic  character  but  its  lustre,  being  in 
chemical  properties  and  natural  affinities  associated  with 
phosphorus. 

630.  The  Chlorid  of  Arsenic  (AsCl3)  is  a  fuming  volatile 
liquid,   decomposed   by  water,  and    very   poisonous.      The 
bromid   and   iodid  are  both  crystallizable  solids,  also  decom- 
posed by  water. 

The  sulphurets  of  arsenic  are  natural  compounds,  used 
as  pigments,  and  also  in  pyrotechny.  The  first,  AS2,  is  a 
red  transparent  body  called  realgar,  and  AsS3  is  the  golden 
yellow  orpiment.  Both  these  substances  are  found  native, 

629.  How  is  arsenic  acid  obtained  ?  To  what  other  acid  is  it 
allied,  and  how  ?  What  is  the  real  character  of  arsenic  ?  630. 
Describe  the  sulphurets. 


336  METALLIC   ELEMENTS. 

and  as  usually  associated,  they  are  brought  from  Koordistan 
in  Persia,  and  from  China.  The  higher  sulphurets  may  be 
formed,,  which  are  AsO5  and  AsO9;  the  former  is  the  product 
thrown  down  by  sulphureted  hydrogen  in  a  solution  of  arse- 
nic. All  but  the  highest  of  these  compounds  are  sulphur  acids. 

631.  Arseniureted  Hydrogen. — This  is  perhaps  the  most 
deadly  poison  known.     Jt  is  a  gas  produced  by  the  action 
of  dilute  sulphuric  acid  on  an  alloy  of  zinc  and  arsenic,  or 
by   the  evolution  of  hydrogen   in   presence  of  arsenic   or 
arsenious  acid.     This  gas  is  readily  absorbed   by  a  solution 
of  sulphate  of  copper,  and  precipitates  an  arseniuret  of  that 
metal.     It  burns  with  a  peculiar   blue  flame,  and  deposits 
metallic  arsenic  or  arsenious  acid.     Marsh's  test  for  arsenic 
depends  on  the  generation  of  this  gas. 

632.  Detection  of  Arsenic  as  a  Poison. — The  fearful  use 
which  is  made  of  this  terrible  poison  in  destroying   human 
life,  renders  it  of  the  first  moment  that  we  should  know  easy 
and  certain  process  for  its  detection.     Accordingly  we  find 
that  very  numerous   methods  have  been  proposed   for  this 
purpose,  a  few  of  which  we  will   briefly  mention.     When  a 
fluid,  or  other  substance  free  from  organic  matter,  is  to  be 
examined   for  arsenic,  there  are   many  tests  which  we  can 
apply.     (1.)  Sulphureted  hydrogen  throws  down  the  yellow 
sulphuret  in  acidulated  solutions  of  arsenious  acid ;    this  is 
redissolved  by  ammonia,  and  again  precipitated  by  acids.    (2.) 
Nitrate  of  silver  produces  a  yellow  precipitate  of  arsenite 
of  silver  in  solutions  of  arsenious  acid,  if  a  trace  of  ammo- 
nia is  present ;  but  the  precipitate  does  not  appear  in  an  acid 
solution,  and  an  excess  of  ammonia  dissolves  it.     (3.)  Sul- 
phate of  copper  gives  a  brilliant  green  precipitate  of  arsenite 
of  copper,  (Scheele's  green,)  in  alkaline  solutions  of  arse- 
nious acid,  which  precipitate  is  redissolved  by  ammonia  in 
excess.     (4.)  A  clean  slip  of  metallic  copper  placed  in  a 
solution  of  arsenious  acid,  is  soon  coated  with  a  gray  deposit 
of  metallic  arsenic ;  this  is  known  as  Remsch's  test. 

633.  All   these  tests   taken  collectively,  constitute  to  the 
mind  of  the  chemist  a  perfect  demonstration  of  the  presence 
of  arsenic ;  but  they  are   liable  to  many  objections  arising 
from  the  presence  of  organic  matters,  of  impurity  in  reagents, 


631.  What  are  the  characters  of  arseniureted  hydrogen  ?  632. 
What  are  some  of  the  means  of  detecting  the  presence  of  this 
poison  ? 


ARSENIC.  337 

and  from  the  possible  presence  of  other  metallic  matters,  as 
antimony,  which  forms  a  brick-red  or  yellowish  sulphuret, 
and  cadmium,  whose  sulphuret  much  resembles  orpiment. 
It  is  therefore  always  demanded  in  judicial  investigations, 
that  no  proof  of  the  presence  of  arsenic  shall  avail  except 
that  of  sublimed  metallic  arsenic. 

634.  Reduction  of  Arsenic. — When  it  is  possible  to  obtain 
from  the  suspected   substance  any  grains  of  arsenious  acid, 
these  are  carefully  selected  for  the  purpose  of  examination. 
If  not,   the  yellow  sulphuret  obtained   from   the   suspected 
solution  by  sulphureted  hydrogen  is  employed,  to  produce 
the  metallic  arsenic.    Either  of  these  substances  is  introduced 
into  a  small  tube  of  hard  glass,  drawn  out  at  the  lower  part 
as   here  represented,  and  the  narrow  part  of  the 

tube  is  then  filled  with  black  flux  to  the  shoulder,  (a.) 
Its  interior  being  wiped  out,  the  flame  of  a  small 
spirit-lamp  is  applied  to  the  upper  part  of  the  mixture 
to  expel  any  moisture  it  may  contain,  which  is  next 
carefully  removed  by  bibulous  paper.  The  flux  is 
then  gradually  heated  to  redness  from  a  to  6,  and 
the  heat  slowly  carried  down  below  &,  until  the 
lower  part  of  the  tube  is  fully  red.  If  any  arsenic 
is  present  it  is  sublimed,  and  deposited  in  a  brilliant 
ring  just  above  the  shoulder,  as  seen  in  the  figure. 
For  further  proof,  the  tube  may  be  drawn  off  at  a 
in  the  lamp-flame,  and  the  metallic  arsenic  vola- 
tilized by  the  heat  until  it  is  all  converted  into 
arsenious  acid,  which  a  magnifier  shows  to  be  in 
brilliant  white  octahedral  crystals. 

635.  But  the  most  common  and   most   difficult  case  of 
testing  for  arsenic  is  when  the  fluids  of  the  stomach,  ejected 
by  the  patient,  or  the  stomach  itself  and  its  contents,  are  to 
be   examined.     The   organic    matters   present   in    all   such 
cases,  render  the  liquid  tests  quite  worthless,  and  oblige  us  to 
have  recourse  to  a  method  of  which  a  brief  sketch  only  can 
be  presented.     The  suspected  fluid,  and   the  solid  parts  cut 
small,  are   placed   in  a  large  porcelain  capsule  with  a  con- 
siderable quantity  of  pure  hydrochloric  acid,  and  as  much 
water  as   will   make   the  mixture   thin.      This   mixture  is 


633.  What  other  bodies  resemble  it  in  its  reactions  ?     634.  How 
are  we  to  obtain  it  in  a  metallic  state  ?     635.  How  do  we  ascertain 
its  presence  when  mixed  with  organic  matters  ? 
29 


338  METALLIC   ELEMENTS. 

heated  on  a  water-bath,  and  while  hot,  small  portions  of  20 
or  30  grains  of  chlorate  of  potash  are  added  to  the  mixture, 
at  short  intervals.  The  chlorine  evolved  by  this  treatment 
completely  decomposes  the  organic  matters,  and  the  final 
result  is  the  production  of  a  yellow  transparent  fluid,  which 
can  easily  be  filtered.  From  this,  sulphureted  hydrogen  in 
excess  will  throw  down  all  arsenic,  antimony,  &c.,  which 
may  be  present ;  and  after  resolution  and  reprecipitation,  the 
suspected  sulphuret  of  arsenic  may  be  reduced  in  the  same 
way  as  has  been  just  described.  Another  mode  of  reduction, 
however,  is  much  to  be  preferred,  where  cyanid  of  potassium 
is  employed  in  the  reduction  tube,  in  place  of  the  black 
flux,  with  about  three  parts  dry  carbonate  of  soda,  and  the 
sulphuret. 

636.  Marsji's  test  is  one  which  is  very  convenient,  sim- 
ple, and  if  used  with    care,  satisfactory  in   most   cases.     It 

depends  on  the  formation  of  arseniureted  hy- 
drogen. The  suspected  substance  is  placed  in 
a  flask  with  the  materials  to  generate  hydrogen, 
(376.)  This  gas,  as  it  issues  from  a  jet,  is  set 
on  fire,  and  if  arsenic  is  present  in  the  mix- 
ture, the  flame  burns  with  a  peculiar  blue 
light,  and  a  clean  plate  of  mica  or  porcelain 
held  over  it,  is  at  once  blackened  by  a  film 
of  metallic  arsenic.  The  annexed  figure 
shows  a  convenient  form  of  this  apparatus. 
The  materials  for  hydrogen  and  the  suspected 
body  are  put  in  the  lower  bulb,  and  dilute  sul- 
phuric acid  being  turned  into  the  upper  bulb, 
hydrogen  gas  is  generated,  and  may  be  delivered  at  will  by 
the  stop-cock  and  jet.  Extremely  minute  traces  of  arsenic 
may  be  detected  by  this  test.  Antimony  presents  a  some- 
what similar  spot,  but  may  easily  be  distinguished  from  arse- 
nic by  a  practised  eye.  It  must  be  observed  that  all  the 
reagents  employed  in  this  apparatus,  the  zinc,  the  acid,  and 
even  the  glass  of  the  vessel,  may  contain  arsenic. 

49.    OSMIUM. 

637.  Osmium  (Os,    99-56)    is   one  of   the   rare    metals 
which  are  associated  with  platinum.     It  has  a  density  of  10-, 

636.  Describe  Marsh's  test.     What  objections  are  there  to  his 
method  ?     637.  With  what  body  is  osmium  associated  ? 


MERCURY.  339 

and  is  of  a  white-bluish  color,  neither  fusible,  nor  volatile,  but 
takes  fire  in  the  air,  forming  osmic  acid,  (OsO4))  which  is 
volatile  and  poisonous.  Osmium  forms  four  oxyds,  viz : 
OsO,  Os2O3,  OsO2,  and  OsO4.  Osmiate  of  potash  is  formed 
when  the  metal  is  fused  with  nitre.  Osmium  combines  with 
sulphur  and  phosphorus,  and  has  the  same  number  of  sulphu- 
rets  as  of  oxyds  and  chlorids. 


CLASS  VI.    NOBLE  METALS,  WHOSE  OXYDS  ARE  RE- 
DUCED BY  HEAT  ALONE. 

50.    MERCURY. 

Equivalent,  101-26.     Symbol,  Hg,  (Hydrargyrum.)     Den- 
sity, 13-5. 

638.  This   is  the  only  metal  which  is  fluid  at  ordinary 
temperatures.     It  is  found  as  native  or  running  mercury  in 
Spain  and  Carniola,  and  also  as  cinnabar  or  sulphuret  of  mer- 
cury, but  it  is  a  rather  rare  and  costly  metal.     It  has  never 
been  found  in  this  country.     The  alchemists  supposed  it  to 
be  silver  enchanted,  (quick-silver,)  and  made  many  efforts  to 
obtain  from  it  the  solid  silver  it  was  supposed  to  contain. 

Pure  mercury  is  a  silver-white,  fluid  metal,  unchanged  by 
air,  and  very  brilliant.  Cooled  below  — 40°,  as  when  frozen 
by  carbonic  acid,  (137,)  it  solidifies,  and  is  then  as  malle- 
able as  lead.  It  crystallizes  at  this  degree  of  cold  in  cubes. 
It  boils  at  660°,  and  forms  a  colorless,  very  dense  vapor. 
Even  at  60°,  a  very  rare  vapor  of  metallic  mercury  (129) 
rises  from  it.  If  heated  in  the  air  at  above  600°,  it  slowly 
passes  to  the  condition  of  red  oxyd  of  mercury,  which  is  its 
highest  combination  with  oxygen. 

639.  The  uses  of  mercury  are  numerous  and  important 
in  the  arts,  and  also  in  medicine.     It  forms  alloys  (amal- 
gams) with   many  other  metals ;  with   tin   it  constitutes  the 
brilliant  coating  of  glass  mirrors,  (called  silvering,)  and  it  is 
of  indispensable   importance   in    procuring   gold  and  silver 
from  their  ores.     Its  use  in  filling  thermometers  and  baro- 
meters (76)  has  already  been  described. 

What  are  its  properties  ?  What  oxyds  does  it  form  ?  What  is 
the  sixth  class  of  metals  ?  638.  How  is  mercury  found  in  nature  ? 
What  are  its  properties  ?  639.  What  are  the  uses  of  this  metal  ? 


340  METALLIC    ELEMENTS. 

Nitric  acid  dissolves  mercury  very  rapidly  even  in  the 
cold ;  hydrochloric  acid  scarcely  acts  on  it,  and  sulphuric 
only  by  the  aid  of  heat,  when  it  forms  an  insoluble  sul- 
phate of  mercury,  evolving  sulphurous  acid,  (286.)  The 
equivalent  of  mercury  is  often  stated  at  202-52,  on  the  sup- 
position that  the  gray  oxyd  is  the  protoxyd  ;  but  this  seems 
to  be  more  properly  considered  as  a  suboxyd,  and  the  real 
protoxyd  as  the  red  oxyd.  On  this  view  the  equivalent  is 
stated  at  101-26. 

Mercury  may  be  so  finely  divided  as  to  lose  its  metallic 
appearance  entirely ;  as  in  blue  pill,  mercurialized  chalk, 
(creta  cum  hydrargyro,)  and  mercurial  ointment,  which  do 
not,  as  has  sometimes  been  stated,  contain  the  suboxyd  of 
mercury,  but  only  mercury  in  a  state  of  very  minute  mechan- 
ical division. 

640.  The  Gray,  or  Suboxyd  of  Mercury ',  Hg2O,  is  formed 
by    digesting   calomel    in  caustic  potash,  or  by  adding  the 
same  reagent  to  a  solution  of  the  nitrate  of  the  suboxyd  of 
mercury.     It  is  an  insoluble,  dark  gray  powder,  which  is 
easily  decomposed  into  metallic  mercury  and  the  red  oxyd. 

The  Red  Oxyd,  or  Protoxyd,  Red  Precipitate,  HgO,  is 
prepared  in  the  large  way  by  heating  the  nitrate  very  cau- 
tiously, until  it  is  quite  decomposed,  and  a  brilliant  red  crys- 
talline powder  is  left.  It  may  also  be  formed  by  heating 
metallic  mercury  for  a  long  time  in  a  glass  vessel  nearly 
closed,  and  in  this  form  is  the  preparation  to  which  the  old 
name  of  red  precipitate  per  se  was  applied.  Heat  decom- 
poses this  oxyd  into  oxygen  and  metallic  mercury.  It  is, 
like  the  oxyd  of  lead,  slightly  soluble  in  water,  and  gives 
to  it  an  alkaline  reaction.  It  is  a  dangerous  corrosive 
poison. 

641.  The  chlorids  of  mercury  correspond  to  the  oxyds, 
and  are  both  very  important  compounds. 

(1.)  The  Subchlorid  of  Mercury,  (Calomel,)  Hg2Cl,  is  a 
well  known  medicine,  and  is  easily  formed  by  precipitating  a 
solution  of  subnitrate  with  common  salt.  A  white,  insolu- 
ble, tasteless  powder  falls,  which  is  the  calomel.  Even  strong 
acids  when  cold  do  not  affect  it ;  but  it  is  instantly  de- 
composed by  alkalies  and  the  suboxyd  produced.  Heat 


How  do  acids  act  upon  it  ?  610.  How  many  oxyds  does  mercury 
form  ?  Describe  the  preparation  of  the  red  oxyd  ?  641.  How  many 
chlorids  are  there  ?  How  is  calomel  prepared  ? 


MERCURY.  341 

sublimes  it  unchanged.  Its  complete  insolubility  at  once 
distinguishes  this  safe  and  mild  substance  from  the  highly 
poisonous — 

(2.)  Corrosive  Sublimate,  or  Chlorid  of  Mercury,  HgCl. 
— This  salt  is  most  economically  prepared  by  the  double  de- 
composition of  sulphate  of  mercury,  by  common  salt,  which 
by  simple  interchange  gives  corrosive  sublimate  and  sulphate 
of  soda,  (HgO,  SO,  +  NaCl=HgCl  +  NaO,SO8.)  The  chlo- 
rid  is  also  formed  by  dissolving  the  red  precipitate  in  hot 
chlorohydric  acid.  Corrosive  Sublimate  is  a  very  heavy 
crystalline  body,  soluble  in  about  15  parts  of  cold  water,  and 
in  two  or  three  parts  of  hot,  giving  a  solution  which  pos- 
sesses the  most  distressing  and  nauseous  metallic  taste, 
and  is  a  deadly  poison.  It  is  soluble  in  alcohol  and  ether. 
It  melts  and  sublimes  a  little  below  600°.  Albumen  com- 
pletely precipitates  it,  and  the  whites  of  eggs  are  therefore 
an  antidote  for  this  poison.  For  the  same  reason  it  is, 
doubtless,  that  timber  and  animal  substances  are  preserved 
from  decay,  as  in  the  kyanizing  process,  by  steeping  in  solu- 
tion of  corrosive  sublimate.  The  albuminous  portions  of 
wood  suffer  decay  sooner  than  the  vegetable  fibre,  and  these 
are  rendered  completely  indestructible  in  the  process  of  Mr. 
Kyan,  which  is  now  in  use  in  our  national  ship-yards. 

642.  There  are  two  iodids  of  mercury,  Hg2l  and  Hgl. — 
The    second    is    a   brilliant    scarlet-red    precipitate,    formed 
by  adding   solution  of  iodid  of  potassium  or  hydriodic  acid 
to  a  solution  of  corrosive  sublimate.     The  iodid  is  at  first  yel- 
low, but  soon  passes  by  a  molecular  change  into  the  splendid 
scarlet  crystalline  powder  before  noticed.     It  cannot  be  used 
as  a  pigment  on  account  of  its  instability. 

643.  Two  sulphurets  of  mercury,  Hg2S  and  HgS,  exist, 
the  first  of  which  is  formed  when  sulphureted  hydrogen  is 
passed  through  a  solution  of  subnitrate  of  mercury,  and  is  a 
black  powder.     The  sulphuret,  HgS,  or  cinnabar,  is  formed 
when    the   nitrate  of  mercury    (nitrate   of  the   red    oxyd) 
is  treated  with  sulphureted  hydrogen.     It  is  a  black  precipi- 
tate, but  turns  red  when  sublimed,  and  forms  the  familiar 


What  is  the  process  for  obtaining  corrosive  sublimate  ?  How  does 
it  differ  from  calomel  ?  Describe  the  antidote  for  this  poison  and  its 
effect  upon  it.  What  uses  are  made  of  chlorid  of  mercury  ? 
642.  Describe  the  iodid  of  mercury.  643.  How  many  sulphurets 
of  mercury  are  there  ? 
29* 


METALLIC    ELEMENTS. 

pigment  vermillion.     This  is  the  common  ore  of  the  quick- 
silver mines. 

644.  The   nitrates   of   mercury. — The  action    of  nitric 
acid  on  mercury  varies  with  the  temperature  and  the  strength 
of  the   acid.     In  the  cold,  dilute   nitric  acid  dissolves  mer- 
cury, forming  a  neutral  nitrate  of  the  suboxyd  ;  but  if  the 
mercury  is  in  excess,  a  salt   is   deposited   in  large  and  trans- 
parent white  crystals,  which  is  a  nitrate  with  excess  of  base. 
If  hot  and  strong,  the  nitrate  of  the  red  oxyd  is  formed, 
which  is  a  very  soluble  salt   not  crystallizable.     A  basic  salt 
of  this  oxyd   may  also  be  formed,  which   is  decomposed  by 
water. 

645.  Sulphate  of  Mercury  (HgO  SO3)   results  as  an  in- 
soluble, white,  subcrystalline  powder,  by  the  action  of  the 
strong  acid  on  metallic  mercury,  (286,)  sulphurous  acid  being 
evolved.     Boiling   water  decomposes    this   salt,  removing  a 
part  of  its  acid,  by  which  a  yellow  basic  sulphate  is  formed, 
known  as  turpeth  mineral.     Its  composition   is  3HgO,  SO3. 
The  sulphate  of  the  gray  oxyd,  Hg2O>  SO3,  is  formed  as  a 
crystalline  white  powder   by  treating  a  solution  of  subnitrate 
of   mercury   with  sulphuric  acid.     It   is  slightly  soluble  in 
water. 

646.  Ammonia    produces    many    interesting   compounds 
with  the  salts  of  mercury,  of  which  the  white  precipitate,  as 
it  is  called,  is  best  known.     This   falls  when  chlorid  of  mer- 
cury in  solution  is  treated  with  ammonia  in  excess,  and  is 
considered  as  a  double  amide  and  chlorid  of  mercury,  HgCl 
and  HgNH2. 

All  the  compounds  of  mercury  are  volatile  at  a  red  heat, 
and  those  which  are  soluble,  whiten  a  slip  of  clean  copper  by 
depositing  metallic  mercury  on  its  surface. 

51.    SILVER. 

Equivalent,  108-12.  Symbol,  Ag,  (Argentum.)  Density,  10-5. 

647.  The   mines   of    Mexico   and    the   Southern   Andes 
furnish    most  of  the   silver   of  commerce,  although    many 
mines   of  this    metal  are  found  in  Spain,  Saxony,  and  the 


What  is  vermillion  ?  644.  How  are  the  nitrates  of  mercury  ob- 
tained ?  What  is  the 'nature  of  the  nitrate  of  'the  red  oxyd  ?  645. 
How  is  the  sulphate  formed  ?  646.  What  is  the  nature  of  white  pre- 
cipitate ?  What  are  the  characteristics  of  mercurial  compounds  ? 
647.  From  what  sources  is  silver  obtained  ? 


SILVER.  343 

Hartz  mountains.  Galena,  or  the  native  sulphuret  of  lead, 
is  also  a  constant  source  of  silver,  as  it  is  rarely  quite  free 
from  this  precious  metal.  Silver  is  often  found  native,  and 
also  in  combination  with  sulphur. 

The  brilliant  lustre  and  white  color  of  this  valuable  metal 
are  familiar  to  all.  It  is  perfectly  ductile  and  malleable,  and 
in  hardness  stands  between  gold  and  copper.  For  the  pur- 
poses of  economy  and  in  coinage  it  is  essential  to  alloy  it 
with  about  -^  part  of  copper,  to  render  it  sufficiently  stiff  and 
hard. 

Pure  silver  melts  at  1873°,  and  when  melted  absorbs  sev- 
eral times  its  volume  of  oxygen  gas,  which  it  parts  with 
again  on  cooling.  This  renders  silver  a  difficult  metal  to 
cast,  and  occasions  the  little  projections  and  roughness  usu- 
ally seen  on  silver  which  has  been  melted. 

Silver  is  obtained  pure  from  its  solution  in  nitric  acid  by 
precipitation  with  metallic  copper,  as  a  finely  divided  crystal- 
line powder  ;  or  by  decomposing  its  chlorid  by  fusion  with 
two  parts  of  dry  carbonate  of  potash.  Nitric  acid  dissolves 
silver  in  the  cold  with  great  rapidity,  and  if  it  contains  any 
gold,  this  is  left  undissolved  as  a  brown  powder. 

Hydrochloric  acid  scarcely  acts  on  silver,  and  sulphuric 
acid  only  when  hot,  forming  the  sulphate  of  silver,  which  is 
sparingly  soluble  in  water. 

648.  Silver   is    parted   from  galena,  by  a  process  called 
cupellation,  or  fusing  at  a  white  heat  the  pulverized  galena 
and  a  certain  quantity  of  metallic  lead,  on  a  little  thick  cup 
or  cupel  of  bone-ashes,  in  a  muffle  exposed   to  a  current  of 
air.     The  lead  oxydizes  and  is  absorbed,  while  the  silver  is 
left  in  a  brilliant  metallic  button  on  the  cupel.     In  the  large 
way  this  process  is  much  facilitated  by  the  fact  that  the  alloy 
of  silver  and  lead  is  more  fusible  than  pure  lead,  and   the 
latter  on  cooling  separates  from  the  former,  which  may  be 
drawn  off,  and  contains  all  the  silver.     This  small  portion  is 
cupelled,  while  the  great  bulk  of  the  lead  is  returned  to  the 
arts  uninjured. 

649.  Three  oxyds  of  silver  are   known  by  chemists ;  the 
suboxyd,   Ag2  O ;    the  protoxyd,   AgO ;    and   the  peroxyd, 
AgO2.     We    will  now    notice  only  the  protoxyd.     This   is 
formed  when  the  solution  of  silver  in   nitric  acid  is  saturated 

What  are  the  characteristics  of  pure  silver  ?  648.  How  is  it  sepa- 
rated from  lead  ?  649.  Describe  the  preparation  and  character  of 
oxyd  of  silver. 


344  METALLIC    ELEMENTS. 

with  caustic  potash,  or  when  the  chlorid  of  silver  recently 
precipitated  is  digested  in  a  solution  of  caustic  potash  of  den- 
sity 1'3.  It  is  a  dark  brown  or  black  powder,  if  prepared 
by  the  first  mode,  or  quite  black  and  dense  by  the  second 
process.  It  is  a  base  forming  well  defined  salts.  Ammonia 
dissolves  it  readily,  and  it  is  also  somewhat  soluble  in  water, 
to  which  it  gives  an  alkaline  reaction.  It  is  easily  reduced 
by  heat  alone.  Its  solutions  are  at  once  detected  by  the 
bulky  white  curdy  precipitate  which  they  form  with  hydro- 
chloric acid  or  with  common  salt.  This  white  precipitate 
turns  dark  by  exposure  to  light. 

650.  Chlorid  of  Silver,  AgCl,  is  formed,  as  just  remarked, 
when  any  soluble  salt  of  silver  is  treated   with   a  soluble 
chlorid  or  with  hydrochloric  acid.     This  substance  fuses  at 
a   moderate   red  heat  into  a  transparent  pale  yellow  fluid, 
which   is   horny  and    tough  when   solid,  and   hence  called 
horn  silver,  a  form  in  which  this  metal  is  sometimes  found  in 
mines.     It   is   easily  reduced   to   the   metallic  state  by  the 
nascent  hydrogen  generated  when  zinc  is  acted  on  by  dilute 
sulphuric  acid  in  contact  with   the  chlorid.     Pure  silver  and 
chlorid  of  zinc  result ;  or,  it  may  be  reduced  by  fusion  with 
twice  its  weight  of  carbonate  of  soda  or  potash. 

The  iodid  and  bromid  of  silver  are,  like  the  chlorid,  insolu- 
ble in  water,  and  very  sensitive  to  light.  The  Daguerreotype 
and  calotype  (62)  are  both  dependent  on  the  sensitiveness 
of  these  compounds  to  light,  for  the  accuracy  and  beauty  of 
their  results. 

The  sulphurets  of  silver  are  found  native,  and  the  tarnish 
which  blackens  silver  articles  on  long  exposure,  is  formed  by 
sulphureted  hydrogen  in  the  air. 

651.  The  Nitrate  of  Silver,  AgO,  NO5,  is  a  salt  which 
crystallizes  in  beautiful  flattened  tables  of  a  hexagonal  form, 
which  dissolve  in   half  their  weight  of  hot  water.     By  heat 
it   fuses,  and  when  cast   in    cylindrical   moulds    forms  the 
slender  sticks  called  lunar  cavstic,  so  much  used  by  the  sur- 
geon.    Its  solution  has  a  disgusting  metallic  taste  even  when 
very  dilute,  and  is  a  most  delicate  test  of  the  presence  of 
chlorine  or  any  of  its  compounds.     It  blackens  rapidly  in 


650.  Describe  the  chlorid.  How  can  it  be  reduced  ?  What  are 
the  relations  of  the  silver  compounds  to  light  ?  What  is  the  action  of 
sulphureted  hydrogen  on  silver  ?  651.  Describe  the  nitrate.  What 
are  its  reactions  ? 


GOLD.  345 

contact  with  organic  matter  when  exposed  to  the  light,  and 
forms  an  indelible  ink,  which  is  much  used  in  marking 
linen.  Solution  of  cyanid  of  potassium  will  remove  the 
stain  produced  by  nitrate  of  silver.  Metallic  copper  at 
once  throws  down  metallic  silver  from  the  nitrate,  and  solu- 
tion of  nitrate  of  copper  is  formed.  Mercury  precipitates 
metallic  silver  from  a  dilute  solution,  in  beautiful  tree-like 
forms,  called  arbor  Diana.  Ammonia,  by  acting  on  pre- 
cipitated oxyd  of  silver,  forms  a  fulminating  compound.  It 
is  extremely  hazardous  to  deal  with,  as  it  explodes  even 
when  wet. 

52.  GOLD. 
Equivalent,  09.44.     Symbol,  Au.     Density,  19-26. 

652.  This  valuable  metal  is  found  only  in  the  metallic  or 
native  state,  being  very  widely  diffused  in  small  quantities  in 
the   older   rocks.     From   these,   by    the   action   of  various 
causes,  it  finds  its  way  into  the  sand   of  rivers,  and  is  dis- 
tributed in  small  quantities,  in  many  wide-spread  deposits  of 
coarse  gravel  or  shingle, — as  on  the  eastern   flanks  of  the 
Ural  Mountains,  and  over  a  wide  belt  of  country  in  Virginia, 
the  Carolinas,  Georgia,  and  Alabama.     These  diluvial  de- 
posits furnish  nearly  all  the  gold  of  commerce,  by  a  process 
of  washing,  and  amalgamation  with  mercury.    Large  masses 
of  gold   sometimes  occur,  as  one  of  twenty-eight   pounds  in 
North  Carolina,  and   in   Siberia  a  mass  was  found,  now  in 
the   Imperial   Cabinet   of  St.    Petersburg,   weighing   nearly 
eighty  English   pounds.     Generally,  however,  k  occurs  only 
in   minute  grains.     It  is  also   found   in  veins  of  quartz,  in 
compact  limestone,  and   distributed  in  iron  pyrites.     Native 
gold  is  usually  alloyed  with  silver. 

653.  Gold  is  distinguished   by  its  splendid  yellow  color, 
its   brilliancy,  and   freedom   from  oxydation,  by  its  extreme 
malleability  and  ductility,  by  its  high  specific  gravity,  (19-26 
to  19-5,)  and  by  its  indifference  to  nearly  all  reagents.     It 
fuses    at    2016°  F.,  and  is  dissolved  only  by  aqua   regia, 
(420,)  by  nascent  cyanogen,  and  by  selenic  acid.     The  first 
is  the  solvent  commonly  known,  and   the  solution  contains 
the  perchlorid  of  gold. 

What  is  the  arbor  Diana  ?  652.  How  does  gold  occur  in  nature  ? 
How  is  it  obtained?  653.  Describe  this  metal.  What  is  its  usual 
solvent  ? 


346  METALLIC    ELEMENTS. 

654.  Gold  forms  two  very  unstable  oxyds,  (Au2O  and 
Au203,)  which  are  decomposed,  even   by  light.     Two  cor- 
responding chlorids  exist.      The  perchlorid  is  a  very  deli- 
quesgent   salt,   forming  a  red    crystalline   mass,   soluble  in 
ether,   alcohol,  and   water.      Metallic    gold   is  deposited  in 
elegant  crystalline  crusts  from  the  ethereal   solution  of  the 
chlorid.     Ammonia  throws  down   from  solutions  of  gold'  an 
olive-brown    powder,   (fulminating   gold,)   which   when   dry 
explodes  with  heat,  or  by  percussion. 

655.  The  solution  of  protosulphate  of  iron  throws  down 
gold  from  its  solutions  in  a  very  fine  brown  powder,  which 
is  green,  as  seen  by  transmitted  light,  when  diffused  in  water. 
The  protochlorid  of  tin   forms  a  characteristic   purple  pre- 
cipitate in  gold  solutions,  called  the  purple  of  cassius,  which 
is  used  in  porcelain  painting,  and  is  probably  a  compound  of 
the  oxyds  of  tin  and  gold.     Gilding  of  ornamental  work  is 
usually  performed  by  gold  leaf;  but  other  metals  are  gilded 
either  by  applying  it  as  an  amalgam   with  mercury,  the 
mercury  being  afterwards  expelled  by  heat,  or  preferably  by 
the  now  process  of  galvanic  gilding  from  a  solution  of  the 
cyanid  of  gold  and  potassium,  (248.)     Gold  wash,  as  it  is 
called,  is  applied  by  a  mixture  of  carbonate  of  soda  or  potash 
in  excess,  with  oxyd  of  gold,  in  which  small  articles  cleansed 
in  nitric  acid  are  boiled,  and  thus  become  perfectly  covered 
with  a  very  thin  film  of  gold. 

53.    PLATINUM. 

Equivalent,  98.68.    Symbol,  PI.    Density,  19.70  to  21-23. 

656.  Platinum    is   a   very    remarkable    metal,  and    if 
abundant  would   be  extensively  useful  in  domestic  economy. 
It  is  found  native  in  the  gold  workings  in  South  America  and 
in   Siberia,  on  the  eastern  slope  of  the  Urals.     No  ore  of 
platinum  is   known,  except   its  alloy  with  gold,  and  with 
iridium,  osmium,  and  rhodium. 

Platinum  is  a  white  metal,  between  tin  and  steel  in  color, 
but  harder  than  gold  or  silver,  and  unless  quite  pure,  is, 
when  unannealed,  nearly  as  hard  as  palladium.  A  very 
little  rhodium  or  iridium  renders  it  more  gray  in  color,  and 


654.  How  many  oxyds  of  gold  are  there  ?  Describe  the  per- 
chlorid. 655.  What  tests  distinguish  gold  ?  How  is  gilding 
effected  ?  656.  Where  is  platinum  found  ? 


PLATINUM.  347 

much  harder.  If  pure  it  is  very  malleable,  especially  when 
hot,  and  can  then  be  imperfectly  welded.  Its  ductility  and 
tenacity  are  remarkable ;  but  its  most  valuable  property  is 
its  infusibility,  which  is  so  great  that  the  thinnest  platinum 
foil  may  be  safely  exposed  to  the  most  intense  heat  of  a 
wind-furnace.  It  is  soluble  only  by  aqua  regia,  but  alloys 
readily  with  lead,  iron,  and  other  base  metals,  so  that  great 
care  is  needed  in  using  platinum  vessels,  not  to  heat  them  in 
contact  with  any  metal  or  metallic  oxyd  with  which  they 
combine ;  caustic  potash,  and  phosphoric  acid  in  contact 
with  carbon,  will  also  act  upon  platinum,  at  a  red  heat. 
This  is  a  most  useful  metal  to  the  chemist,  and  vessels  of 
platinum  are  quite  indispensable  in  the  operations  of  analysis. 
Large  retorts  or  boilers  are  made  of  it  for  the  use  of  manu- 
facturers of  sulphuric  acid,  which  sometimes  hold  sixty  or 
more  gallons.  In  Russia  it  has  been  employed  in  coinage, 
for  which  by  its  great  density  and  hardness  it  is  well  suited. 
When  recently  fused  by  the  compound  blowpipe  or  the  gal- 
vanic focus,  its  density  is  about  19'9,  which  is  increased  to 
21-5  by  pressure  and  heat. 

657.  Platinum  is  obtained  pure  by  digesting  crude  plati- 
num in  aqua  regia,  and  adding  to  the  deep  brown  liquid  a 
solution  of  chlorid  of  ammonium ;  this  throws  down  an  orange- 
colored  precipitate,  which  is  a  double  chlorid  of  platinum 
and  ammonium.  This  precipitate  is  reduced  by  heat  to  the 
metallic  state, — a  porous  dull  brown  mass,  commonly  known 
as  platinum  sponge.  All  the  platinum  of  commerce  is  treated 
in  this  way.  The  sponge  is  condensed  in  steel  moulds  by 
heat  and  pressure,  and  when  compact  enough  to  bear  the 
blows  of  the  hammer,  is  heated  and  forged  until  it  is  perfectly 
tough  and  homogeneous. 

Spongy  platinum  is  a  very  remarkable  substance,  having, 
as  already  noticed,  (397,)  power  to  cause  the  combination  of 
hydrogen  and  oxygen,  and  to  effect  other  chemical  changes 
without  being  itself  altered. 

Platinum  black  is  a  still  more  curious  form  of  metallic 
platinum,  and  is  formed  by  electrolyzing  a  weak  solution 
of  chlorid  of  platinum,  when  the  black  powder  of  platinum 
will  appear  on  the  negative  electrode.  The  silver  plates  in 
Smee's  battery  (247)  are  prepared  in  this  way.  It  is  also 

Describe  its  characters  and  uses.  657.  How  is  it  obtained  from 
its  ores  ?  What  is  platinum  black,  and  what  are  its  properties  ? 


348  METALLIC    ELEMENTS. 

prepared  by  adding  an  excess  of  carbonate  of  soda,  with 
sugar,  to  a  solution  of  chlorid  of  platinum,  and  gradually 
heating  the  mixture  to  near  212°,  stirring  it  meanwhile. 
The  black  powder  which  falls  is  afterwards  collected  and 
dried.  This  powder  has  the  property  of  causing  union  among 
gaseous  bodies — as,  for  example,  the  elements  of  water — to  a 
greater  degree  than  the  spongy  platinum. 

658.  Platinum   forms  two  oxyds,  and  two  chlorids,  viz  : 
P1O,  P102,  and  P1C1,  PICI2.     The  oxyds  are  prepared  from 
the  chlorids  by  precipitation  with  alkalies,  and  are  very  unsta- 
ble.    The  protochlorid  is  prepared  by  heating  the  bichlorid 
to  450°,  when  chlorine  is  evolved  and  it  is  left  as  a  greenish- 
gray  insoluble  powder. 

The  bichlorid  of  platinum  is  the  usual  soluble  form  of 
platinum,  and  is  always  formed  when  platinum  is  digested 
in  aqua  regia.  It  is  prepared  pure  by  dissolving  spongy 
platinum  in  this  menstruum,  and  cautiously  expelling  the 
acid  by  evaporation,  at  a  moderate  temperature.  It  gives 
a  rich  orange  solution  both  in  alcohol  and  water ;  and 
forms  soluble  salts  of  much  interest,  with  many  metallic 
chlorids.  Those  with  the  alkaline  metals  are  the  most  im- 
portant. The  double  chlorid  of  platinum  and  potassium  is 
a  very  sparingly  soluble  salt,  (P1CI2,PC1,)  which  falls  as  a 
yellow  highly  crystalline  precipitate  when  chlorid  of  plati- 
num is  added  to  a  solution  of  chlorid  of  potassium.  The 
double  chlorid  of  sodium  and  platinum  (PlCl2NaCl  +  6HO) 
is  on  the  other  hand  very  soluble,  and  forms  large  beautiful 
yellowish-red  crystals  in  a  dense  solution.  Potash  and 
soda  are  most  easily  separated,  by  the  different  solubility  of 
their  double  chlorids.  The  double  chlorid  of  ammonium  and 
platinum  (P1C12NH4CI)  is  the  orange  precipitate  before  named, 
and  is  the  only  test  required  to  determine  with  perfect  cer- 
tainty the  presence  of  platinum  in  a  solution. 

54.    PALLADIUM. 

Equivalent,  53-27.     Symbol,  Pd.     Density,  11-8. 

659.  This  very  rare    metal    is    usually  found    associated 
with  ores  of  platinum.     It  is  also  found  alloyed  with  gold 

658.  How  is  the  bichlorid  prepared  ?  Describe  the  double  chlorids 
of  platinum  and  the  alkalies,  their  preparation  and  characteristics. 
659.  What  is  the  symbol  and  equivalent  of  palladium  ? 


RHODIUM,    IRID1UM.  349 

and  silver  in  Brazil.  It  is  a  grayish-white  metal,  rather 
more  brilliant  than  platinum,  ductile,  malleable,  and  extreme- 
ly infusible.  It  is,  however,  fused  by  the  compound  blowpipe. 
It  gains  a  blue  tarnish  like  steel  by  heating  in  the  air,  which 
it  loses  by  a  white  heat.  In  hardness  it  is  equal  to  fine  steel, 
and  it  does  not  lose  its  elasticity  and  stiffness  by  a  red  heat. 
Its  density  varies  from  10-5  to  11/8,  and  it  suffers  no  change 
by  exposure  in  the  air.  These  qualities  would  render  it  a 
very  valuable  metal  if  it  could  be  obtained  in  a  sufficient 
quantity.  Nitric  acid  dissolves  it  slowly,  but  aqua  regia 
more  rapidly.  It  forms  two  oxyds  and  two  corresponding 
chlorids. 

55.    RHODIUM. 

Equivalent,  52-4.     Symbol,  R.     Density,  10-8. 

660.  This   is  another  metal  associated  with  the  ores  of 
platinum,  and  is  obtained  by  a  process  which  need  not  be 
described  here.     It  is  a  reddish-white  metal,  as    fusible  as 
iridium,  and  in  hardness,  ductility,  and  malleability,  is  much 
like  it.     Its  density  is  probably  about  10-8.  (Hare.) 

56.    IRIDIUM. 

Equivalent,  98-68.     Symbol,  Ir.     Density,  21-8. 

661.  Iridium  is  also  associated  with  the  ores  of  platinum 
in  the  native  alloy  called  iridosmine,  or  osmiuret  of  iridium, 
which   is   left  in  black  shining  scales  as  a  residuum,  after 
digesting  platinum  ores  in  aqua  regia.     Iridium  when   ob- 
tained pure  and   fused,  is  susceptible  of  a  fine  polish,  has  a 
pale  antimonial  whiteness  and  the  fracture  of  cast-iron.     It 
is  somewhat  ductile,  as  hard  as  unannealed  steel,  and  fuses 
under  the  compound  blowpipe.  .  It  is  the  densest  body  known, 
being  as  high  as  2T80.  (Hare.)     The  native  alloy  is  much 
more  infusible  than  the  pure  iridium,  being,  in  fact,  one  of  the 
most  infusible  bodies  known ;  it  is  very  hard,  and  is  used  to 
point  gold  pens.     Four  oxyds  and  four  chlorids  have  been 
described. 


Describe  its  properties?     660.  What  is  said  of  rhodium  ?     661. 
With  what  metal  is  iridium  associated  ?     What  is  its  density  and 
hardness  ? 
30 


PART  IV.— ORGANIC  CHEMISTRY.* 

INTRODUCTION. 

1.  General  Properties  of  Organic  Bodies. 

662.  Definition. — Organic  chemistry  is  confined  to  the 
study  of  those  bodies  which  are  the  products  of  life,  and  to 
the  changes  which  they  suffer  by  the  action  of  other  sub- 
stances. 

663.  The  constituents  of  organic   bodies   are   compara- 
tively few,  but  the  results  produced   by  their  various  combi- 
nations are  wonderfully  complex  and  numerous.     Oxygen, 
nitrogen,   carbon,  and  hydrogen,  differently  arranged   and 
combined,  compose  nearly  all  the  bodies  found  in  the  vege- 
table and  animal  kingdoms.     Sulphur,  phosphorus,  and  per- 
haps iron,  occasionally  occur,  however,  in  these  products ; 
and  by  the  action  of  various   reagents  we   are   enabled  to 
combine  with  organic  substances,  or  with  the  products   of 
their  decomposition,  chlorine,  bromine,  iodine,  and  various 
other   bodies.     In   this  way  a  great  number  of  new   com- 
pounds are  produced,  which  come  within  the  province  of  or- 
ganic chemistry  as  above  defined. 

664.  Both  animals  and  vegetables  contain  salts  of  potash, 
soda,  lime,  magnesia,  and  iron,  with  sulphuric,  phosphoric,  and 
silicic  acids,  and  chlorine.     Animals  also  secrete  phosphate 
and  carbonate  of  lime,  to  form  their  bones,  as  in  quadrupeds, 
and  their  external  coverings,  as  in  the  mollusca.     These  salts 
have  been  already  described  under  their  proper  heads,  in  the 
inorganic  chemistry,  and   their  relations  to  life  will  be  con- 
sidered in  the  section  on  the  nutrition  of  animals  and  plants. 

665.  A  strictly  philosophical   distinction  cannot  be  estab- 
lished between  organic  and  inorganic  chemistry,  as  it  will 
be  seen  from  the  statements  already  made,  that  these  two 

*  The  questions  at  the  foot  of  each  page  will  be  omitted  in  the 
remaining  portion  of  the  work,  in  the  belief  that  both  teacher  and 
pupil  will,  by  the  time  they  reach  this  point,  have  become  so  familiar 
with  the  subject  and  with  each  other,  as  to  render  the  questions  no 
longer  important,  while  the  space  which  they  occupy  can  be  better 
employed. 


GENERAL    PROPERTIES   OF   ORGANIC   BODIES.  351 

departments   shade   into  each  other  so  gradually,  that   the 
line  of  division  must  of  necessity  be  somewhat  arbitrary. 

Formerly  it  was  considered  as  a  distinctive  mark  of  or- 
ganic compounds,  that  they  could  not  be  artificially  formed 
at  will,  from  a  combination  of  their  constituents.  This 
distinction  is,  however,  no  longer  exclusively  true,  since 
we  are  now  able  to  form  urea  from  cyanic  acid  and  ammo- 
nia, both  of  which  may  be  derived  from  the  reaction  of  the 
mineral  ingredients.  By  peculiar  processes  we  have  also 
been  able  to  form  numerous  other  bodies  which  are  the 
products  of  organic  life.  They  are,  however,  comparatively 
simple  in  their  composition,  and  occur  in  nature  only  as 
secretions  of  organized  bodies.*  No  art  can  ever  enable  us 
to  produce  the  simplest  organized  tissue,  as  a  cell  or  a  fibre. 

666.  An  important  characteristic  of  organized  bodies  is 
the  complexity  of  their  composition,  and  their  high  equiv- 
alent numbers.     In  mineral  compounds  we  rarely  have  any 
thing  more  intricate  than  a  salt  of  two  or  three  bases ;  as  for 
example,  common  alum,  (568,)  which  may  be  resolved  into 
sulphuric  acid,  alumina,  potash,  and  water,  each   of  which 
contains  oxygen   and   a  base.     These  constituents  may  be 
again  combined  to  form  the  original  alum. 

667.  The  substance  called   gelatine,  which  is  a  principal 
constituent  of  the  cellular  tissue  in  animals,  has  the  formula 
C48H41N7Oi8.       By   the    action    of   heat,   or   other   agents, 
we   are   able   to   resolve  this  complex  body  into  ammonia, 
water,  and  other  compounds,  which  are  very  much  more  sim- 
ple  than   gelatine.     And   these   again  we   may  decompose 
into  their  constituent  elements.     But   by  no   power  at   our 
command,  can  we  join  the  dissevered  elements  to  form  ge- 
latine anew.     This  peculiarity  of  organization  is  dependent 
on  the  vital  force,  which  modifies  the  chemical  affinities  of 
bodies  in  a  manner  that  we  can  never  hope  to  imitate.    While, 
therefore,  in  the  study  of  mineral  chemistry  we  can  usually 
avail  ourselves  of  the  evidence  to  be  obtained  from  both  analy- 
sis and  synthesis,  (14,)  in  organic  chemistry  we  must  gener- 
ally be  content  with  the  former  of  these  methods  of  proof. 

668.  Organic  bodies   possess  the  further  peculiarity,  that 
carbon  is  almost  invariably  one  of  their  constituents,  and 

*  Organized  bodies,  or  organisms,  are  distinguished  by  having  a 
structure,  which  is  the  result  of  life ;  this,  organic  bodies  do  not 
necessarily  possess.  For  example,  horn  and  skin  are  organisms, 
while  gum  and  fat  are  simply  organic  bodies. 


352  ORGANIC    CHEMISTRY. 

associated  in  such  proportions  with  oxygen,  nitrogen,  and 
hydrogen,  that  when  the  body  is  burned,  these  last  combine 
with  it  to  form  carbonic  acid  and  carbureted  hydrogen  ; 
and  also  among  themselves,  producing  water  and  ammonia ; 
while  any  excess  of  carbon  remains  behind  as  charcoal. 
Organic  substances  have  for  this  reason  been  defined  by 
some  writers  as  those  bodies  which  char  or  blacken  by  heat. 

2.  Modes  of  Combination. 

669.  The   different   combinations    presented   by  organic 
bodies  may  be  reduced  to  three  classes,  and  the  laws  which 
govern  these  will  equally  apply  to  all  chemical  compounds. 
These  three  modes  of  combination  are  termed,  (1,)  equiva- 
lent  substitution ;    (2,)    substitution    by   residues,    and    (3,) 
direct  union. 

670.  (1.)  Equivalent    Substitution.  — -  The  statement  of 
this  law  is  that  one  or  more  equivalents  of  any  element  in  a 
compound,  may  be  replaced  by  the  same  number  of  equiva- 
lents of  another  element.     For  example,  acetic  acid,  C4H4O4, 
by  the  action  of  chlorine  gas  loses  three  equivalents  of  hydro- 
gen, which  go  to  form   hydrochloric  acid,  and   takes  in  their 
place  three  equivalents  of  chlorine,  which  are  substituted  for 
the  hydrogen.  The  new  product,  (chloracctic  acid,  C4CI3HO4,) 
closely  resembles  acetic  acid  in  its  properties. 

Chlorine  can  then  replace   hydrogen,  and  the  same  power 
is  possessed  by  bromine  and  iodine. 

671.  Alcohol,  which  has  the  formula  C4HcO2,  may  have 
its   oxygen    replaced   by  sulphur,  yielding   sulphur-alcohol, 
C^Sa.     Selenium  and   tellurium,  which    bear    the   closest 
resemblance   in   all  their  properties   to   sulphur,   (250,  iii.) 
can  in  the  same  manner  replace  oxygen.     We  see  then  that 
hydrogen  may  be  replaced  by  chlorine,  bromine,  and  iodine  ; 
and  oxygen  by  sulphur,  selenium,  and  tellurium. 

672.  Where  acetic  acid  acts  upon  metallic  zinc,  hydrogen 
is  evolved  and  acetate  of  zinc  (C4H3ZnO4)  is  formed ;  a  com- 
pound in  which  an  equivalent  of  zinc  replaces  one  of  hydro- 
gen.    When  this  acid  acts  upon  oxyd  of  zinc  the  acetate  is 
also  formed,  while  water  is  produced  by  the  union  of  the 
oxygen  of  the  oxyd  with  the  hydrogen  of  the  acid.     Many 
chemists  suppose  that  the  acid  contains  water  (thus  C4H3O3 
-f  HO,)  which  is  decomposed  in  the  one  case,  and  displaced 
by  the  oxyd  in  the  other :  but  we  cannot  separate  water  from 
the  acid  and  obtain  the  compound  C4H3O3,  and  indeed,  we 


MODES   OF   COMBINATION.  353 

have,  no  proof  of  the  existence  of  such  a  compound.  The 
view  just  stated,  explains  the  constitution  equally  as  well  as 
the  old  one,  and  avoids  all  hypothesis. 

673.  From  acetic  acid  we  may  form  a  great  number  of 
salts  in  which  an  equivalent  of  metal  replaces  one  of  hydro- 
gen, and  the  chloracetic  acid  yields  a  corresponding  series. 
These  constitute  a  genus,  of  which  acetic  acid  is  the  type, 
and  the  various  salts  species.     Thus — 

Acetic  acid,  C4H4O4  Chloracetic  acid,  C4C13H04 

Acetate  of  potash,  C4H3KO4         Chloracetate  of  potash,  C4C13K04 
Acetate  of  silver,     C4H3AgO4       Chloracetate  of  silver,  C4Cl3AgO 

In  some  compounds  we  can  successively  replace  one,  two, 
and  even  five  equivalents  of  hydrogen  by  chlorine,  or 
bromine,  without  deranging  the  molecular  structure  of  the 
compound — m  other  words,  without  destroying  its  type. 

674.  In  tne  acetic  and  many  other  acids,  but  one  equiva- 
lent of  hydrogen  can  be  replaced  by  a  metal,  so  that  the  salts 
contain  but  one  equivalent  of  base ;  these  acids  are  therefore 
called  monobasic  acids.    In  tartaric  acid,  C8H6O,2,  two  equiva- 
lents of  hydrogen  may  be  thus  replaced,  and  a  salt  obtained 
of  the  formula  C8H4MaO12,  M  standing  for  any  metal.     These 
two  equivalents  may  be  replaced  by  two  different  metals,  as 
by  potassium  and  sodium,  C8H4KNaO12 ;  and  salts  may  also 
be  formed  in  which  but  one  equivalent  of  the  hydrogen  is 
replaced,  as  C8H5KO12.     These  are  acid  salts,  having  an  acid 
reaction,  and  are  still  capable  of  neutralizing  alkalies.     Acids 
like  the  tartaric  are  called  bibasic,  and  are  distinguished  both 
by  yielding  acid  salts   and  by  combining  with  two   bases. 
Tribasic  acids  are  also  known,  which  contain  three  equiva- 
lents of  hydrogen,  replaceable  by  a  metal ;  they  can  form  three 
kinds  of  salts,  in  which  one,  two,  and  three  equivalents  of  a 
metal  are  substituted   for  the  same   number  of  hydrogen. 
The  two  first  of  these  salts  are  acid,  the  third  is  neutral. 

675.  (2.)  Substitution  by  Residues.  —  When  nitric 
acid,  NHO6=NO3H-HO,  acts  upon  the  body  called  benzene, 
C12H6,  two  equivalents  of  its  oxygen  combine  with  the 
hydrogen  of  the  benzene  to  form  2HO,  and  the  residues  unite 
to  produce  a  new  body,  nitrobenzide,  C12H5NO4,  or  C12H4 
NHO4.  Acetic  acid  and  alcohol  unite  in  the  same  way  to 
form  acetic  ether,  C4H4O4+C4H6O2  —  2HO=C8H8O4.  In 
these  compounds  the  acids  cannot  be  discovered  by  the  usual 
tests. 

30* 


354-  ORGANIC    CHEMISTRY. 

From  these  and  a  great  number  of  similar  cases,  we 
deduce  the  law,  that  in  these  reactions,  a  portion  of  the 
oxygen  of  one  body  combines  with  the  hydrogen  of  the 
other  to  form  water,  which  is  set  free,  while  the  residues 
unite.  In  the  formation  of  nitrobenzide  NHO6 — O2  is  sub- 
stituted for  H2  in  the  benzene.  This  principle  explains  in  a 
simple  manner  many  reactions  in  chemistry,  and  admits  of  a 
great  number  of  applications,  some  of  which  we  shall 
mention  in  their  appropriate  places. 

676.  The   student    is    now    prepared    to   understand   the 
formation  of  the  sesqui-salts.     In  those  salts,  which  corres- 
pond to  oxyds  with  one  equivalent  of  oxygen,  the  metal  re- 
places the  hydrogen,  equivalent  for  equivalent ;  thus  acetic 
acid  is  C4H4O4,  and   acetate  of  iron,  C4H3FeO4 ;   but  three 
equivalents  of  acetic  acid  react  with  one  of  sesquioxyd  of 
iron  to  form  one  of  sesquiacetate  of  iron  and  three  of  water ; 
three  equivalents  of  hydrogen  are  removed,  and  but  two  of 
iron  combined  in  their  place.    One  equivalent  of  sesquiacetate 
of  iron  contains  C12H9Fe2O12,  while  three  of  the  acetate  equal 
C,2H9Fc3O,2.       The   reaction   which    produces  this   seeming 
anomaly  is  readily  explained :  the  three  equivalents  of  oxgen 
in  the  sesquioxyd  Fo2O3  unite  with  three  of  the  hydrogen  of 
the  acid,  to  form  3HO,  and  the  residue  Fe2  replaces  H3. 

677.  (3.)  The  third  mode  of  combination  in  compounds  is 
that  of  direct  union,  as  when  chlorine  and  sodium  unite  to 
form  common  salt.     We  have  in  organic  chemistry  examples 
of  this  mode  in  the  vegetable  alkalies  which  unite  directly 
with  acids  and  metallic  salts ;  also  in  some  organic  products 
which  combine  in  the  same  manner  with  chlorine. 

3.  Isomerism. 

678.  We  have   first  seen   that  acetic  acid  may  have  its 
hydrogen  replaced  by  chlorine,  while  the  characters  of  the 
compound  remain    unaltered.     From    this   and    similar   in- 
stances we  are  led  to  conclude  that  the   properties  of  com- 
pounds depend  rather  upon  the  peculiar  arrangement  of  their 
constituent  atoms  than  upon  their  kind  :  and  moreover  that 
the  same  proportions  of  the  same  elements  may  by  a  different 
mode  of  union   form   compounds   widely   differing   in  their 
characters.     Such   is  really  the  case ;    there  are  many  in- 
stances of  substances  which,  possessing  the  same  composition 
and  equivalent,  are  yet  perfectly  distinct  in  their  properties. 


ON  THE  DENSITY  OF  VAPORS.  355 

The  formic  ether  of  alcohol,  and  the  acetic  ether  of  wood 
spirit,  are  represented  by  the  same  formula,  i.  e.  C6H6O4, 
but  are  very  different  in  respect  of  many  of  their  properties  ; 
from  the  manner  of  their  formation  and  the  products  of  their 
decomposition,  we  have  evidence  of  a  difference  in  the 
arrangement  of  their  molecules.  Substances  which  have 
the  same  equivalent  composition,  but  which  differ  in  their 
properties,  are  called  isomeric,  or  more  definitely  metameric 
bodies.* 

679.  Another  form  of  isomerism  is  that  in  which    the 
relative  proportions  of  the  elements  being  the  same,  one  sub- 
stance has  double  or  triple  the  equivalent  of  the  other.     The 
oil  of  bitter  almonds  and  benzoine  may  both  be  represented 
by  0,411602,  but  the  equivalent  of  the  last  is  double  that  of 
the  oil,  and  its  real  formula  is  C28H12O4.     This  relation  is 
called  polymeric,  and  benzoine  is  said  to  be  polymeric  of 
bitter  almond  oil. 

The  compounds  of  carbon  and  hydrogen  present  many 
remarkable  instances  of  isomerism ;  olefiant  gas,  C4H4,  buty- 
rene,  C8H8,  naphtene,  C16H,6,  and  cetene,  C^H^,  have  the  same 
proportions  of  carbon  and  hydrogen,  and  each  of  these  is 
polymeric  of  these  before  it.  The  equivalents  of  tlrese 
bodies  are  determined  from  an  examination  of  their  com- 
binations with  other  substances,  or  from  the  density  of  their 
vapors. 

4.   On  the  density  of  vapors. 

680.  It   has   been   already  shown   that   bodies   unite   in 
certain  proportions  by  volume  as  well  as  by  weight,  (190,)  and 
that  where  a  condensation  follows  the  union,  it  is  always  one- 
third,  one-half,  or  some  other  simple  proportional  to  the  sum 
of  the.  volumes  of  its  constituents.     The  vapor  of  water 
contains  two  volumes  of  hydrogen,  and  one  of  oxygen,  con- 
densed one-third,  and  its  specific  gravity  is  equal  to  one-half 
the  sum  of  the  specific  gravities  of  its  constituents,  thus — 
69-3  is  the  density  of  hydrogen,  air  being  1000,  and  on  the 
same  scale  the  density  of  oxygen  is  1109-3,  then — 

*  Isomerism,  from  isos,  equal,  and  meros,  measure,  may  be  employed 
to  designate  all  cases  in  which  the  same  elements  exist  in  the  same 
relative  proportions  ;  while  metamerism,  from  meta,  by,  and  meros, 
implies  that  the  proportions  of  the  elements  are  not  only  relatively 
but  absolutely  the  same.  The  term  polymerism,  from  polus,  many, 
and  meros,  is  explained  by  the  examples  given  in  (679.) 


356  ORGANIC    CHEMISTRY. 

Two  volumes  of  hydrogen,  2  X  69-3         =         138' 6 

One          "  oxygen,  =       1109-3 

Two         "  water,  =       1247-9 

One          "  "  =         623-9 

Now  the  specific  gravity  of  the  vapor  of  water  at  the 
normal  temperature  and  pressure  (120  and  131,)  is  620-1, 
air  being  1000,  consequently  if  we  know  (192)  the  com- 
bining volume  of  any  vapor,  or  the  volume  of  its  elements 
and  its  density,  we  can  calculate  the  number  of  equivalents 
of  each  element  in  the  compound,  or  in  other  words  we  can 
ascertain  its  formula.  For  example,  olefiant  gas  has  a  specific 
gravity  of  971,  air  being  1000,  and  it  is  composed  of  equal 
equivalents  of  carbon  and  hydrogen;  one  volume  of  it 
contains — 

One  volume  of  carbon  vapor,*  =  832-0 

Two  volumes  hydrogen,  2  X  69-3          =  138-6 

Yielding  one  volume  of  olefiant  gas,  970-6 

As  we  know  from  its  compounds  that  the  equivalent  of 
this  gas  is  represented  by  four  volumes,  its  formula  must  be 
C4H4.  The  vapor  of  butyrene  has  a  density  of  1926 ;  and  as 
its  combining  volume  is  the  same  as  olefiant  gas,  its  formula 
will  be  C8Hg.  Cetene,  C^H^,  has  a  density  eight  times  that 
of  olefiant  gas. 

681.  The  determination  of  the  density  of  vapors  is  of 
great  importance:  in  case  of  some  volatile  organic  com- 

*  As  carbon  is  not  volatile,  the  density  of  its  vapor  cannot  be  de- 
termined directly ;  in  its  gaseous  compounds,  however,  we  know 
that  it  must  assume  the  gaseous  form.  Now  carbonic  acid  contains 
a  volume  of  oxygen  equal  to  its  own ;  if  then  from  the  number  ex- 
pressing its  specific  gravity,  we  deduct  that  of  oxygen,  we  shall 
have  the  specific  gravity  of  the  carbon  vapor. 

The  density  of  carbonic  acid  is  1525-2      air  1000 

Deduct  oxygen,  1109-3 

We  have  the  density  of  carbon  vapor,  415-9 
If  we  assume  that  the  acid  contains  two  volumes  of  oxygen  gas 
and  one  of  carbon,  (CO2)  condensed  into  two  volumes,  the  density 
of  the  vapor  will  be  415-9  X  2  —  831-8.  It  is  not  improbable,  how- 
ever, that  the  acid  may  consist  of  equal  volumes  of  carbon  vapor 
and  oxygen  condensed  one-half;  in  which  case  the  density  of  tne 
former  will  be  415-9,  and  its  volume  the  same  as  hydrogen ;  two 
volumes  corresponding  to  an  equivalent. 


ANALYSIS   OF    ORGANIC    SUBSTANCES.  357 

pounds  which  form  no  combinations  with  other  substances  it 
is  the  only  means  of  ascertaining  their  constitution  and 
equivalent.  The  process  is  very  simple;  the  method  em- 
ployed in  case  of  gases  has  been  already  described,  (49.) 
When  the  substance  is  a  liquid  or  solid,  it  is  introduced  into 
a  narrow-necked  glass  globe  of  the  form  represented  in  the 
annexed  figure,  the  weight  of  which  is  care- 
fully ascertained.  The  globe  is  held  by 
means  of  its  handle  firmly  attached  by  wire, 
beneath  the  surface  of  an  oil  or  water-bath, 
and  then  heated  to  some  degrees  above  the 
boiling-point  of  the  substance.  When  this  is 
all  volatilized  and  the  globe  is  filled  with  the 
vapor,  the  open  and  projecting  end  of  the 
globe's  neck  is  sealed  by  the  flame  of  a  spirit 
lamp ;  and  at  the  same  time,  the  temperature 
of  the  bath  is  noted.  When  the  globe  is  cooled 
it  is  again  weighed,  and  the  end  of  the  neck 
broken  off  beneath  the  surface  of  mercuy,  which 
rushes  up  and  fills  the  vacuous  vessel.  The 
mercury  is  then  carefully  measured.  The  capacity  of  the 
vessel  and  its  weight  being  thus  ascertained,  we  can  find  the 
weight  of  a  volume  of  vapor  at  the  observed  temperature, 
and  by  an  easy  calculation  can  determine  what  would  be  its 
volume  at  the  ordinary  temperature,  (88) ;  its  weight  com- 
pared with  that  of  the  same  volume  of  air  gives  the  specific 
gravity  required. 

ANALYSIS  OF  ORGANIC  SUBSTANCES. 

682.  The  ultimate  analysis  of  organic  substances  is  of 
great  importance ;  for  as  we  are  unable  to  form  them  by  a 
direct  combination  of  their  elements,  a  correct  understanding 
of  their  composition  and  of  the  nature  of  the  changes  which 
they  undergo,  must  depend  entirely  on  the  results  of  their 
analysis.  The  equivalent  of  many  substances  is  so  large, 
that  a  change  of  one-hundredth  part  in  the  proportions,  gives 
to  the  compound  entirely  distinct  properties.  Great  refine- 
ment is  consequently  necessary  in  analysis,  to  enable  us  to 
detect  the  minute  differences  in  composition,.and  such  have 
been  the  care  and  skill  with  which  the  subject  has  been 
studied,  that  we  have  now  arrived  at  a  surprising  accuracy 
in  operations  of  this  kind. 


358  ORGANIC    CHEMISTRY. 

683.  In  theory,  the  process  of  organic  analysis  is  ex- 
ceedingly simple^     If  any  organic  substance,  as  sugar,  for 
example,  is  heated  with  a  body  capable  of  yielding  oxygen, 
such  as  the  oxyd  of  copper,  lead,  or  any  other  easily  re- 
ducible metal,  it  is  completely  decomposed ;  the  carbon  and 
hydrogen  take  oxygen  from  the  metallic  oxyd,  and  are  wholly 
converted  into  carbonic  acid  and  water.     From  the  weight 
of  these,  it  is  easy  to  calculate  the  amount  of  carbon  and 
hydrogen  in  the  body,  and  if  it  contains  no  other  element 
except  oxygen,  this  is  known  by  the    loss.     But  notwith- 
standing the  theoretical  simplicity  of  the  process,  its  execution 
is  exceedingly  difficult,  and  very  many  precautions  are  ne- 
cessary to  insure  accuracy.     It  is  not  the  object  of  this  work 
to  explain  all  the  precautions  necessary  to  the  successful  per- 
formance of  analytical  operations,  but  merely  to  give  an 
outline  of  the  method  pursued,  and  a  general  idea  of  the 
means    employed.      For   more  particular   information    the 
student  is  referred  to  an  excellent  memoir  on  this  subject,  by 
Baron  Liebig,  published  in  a  separate  volume. 

684.  The  operation  is  performed  in  a  combustion  tube  of 
hard  glass,  about  12  inches  in  length,  and  from  -j^-  to  -f^  of 
an   inch  in  diameter.     One  end  is  drawn  out  to  a  point, 
turned  aside  and  sealed.     Oxyd  of  copper  prepared  from  the 
nitrate   (609)   is  generally   employed   for   the   combustion. 
Just  before  using  it,  it  is  heated  to  redness,  in  order  to  expel 
the  moisture  which  it  readily  attracts  from  the  atmosphere ; 
the  combustion  tube  is  then  about  two-thirds  filled  with  the 
hot  oxyd.     The  substance  to  be  analyzed  having  been  care- 


\ 


Oxyd.  Mixture.  Oxyd. 

fully  desiccated,  five  or  six  grains  of  it  are  weighed  out  in  a 
tube  with  a  narrow  mouth,  in  order  to  prevent  the  absorption 
of  moisture.  It  is  then  rapidly  mixed  in  a  dry  porcelain 
mortar,  with  the  greater  portion  of  the  oxyd  from  the  tube, 
to  which  it  is  again  transferred,  and  the  tube  is  then  nearly 
filled  up  with  pure  oxyd.  The  relative  portions  of  the  oxyd 
and  mixture  are  shown  in  the  figure  above. 

685.  However  carefully  the  mixture  has  been  made,  a 


ANALYSIS    OF   ORGANIC    SUBSTANCES. 


359 


little  moisture  will  have  been  absorbed  from  the  air,  which 
must  be  removed  by  the  following  arrangement.  To  the 
end  of  the  combustion  tube  is  fitted,  by  means  of  a  cork,  a 
long  tube  filled  with  chlorid  of  calcium,  and  to  this  is  attached 
a  small  air-pump.  The  combustion  tube  is  covered  with  hot 
sand,  and  the  air  slowly  exhausted.  After  a  short  time,  the 
stopcock  is  opened,  and  the  air  allowed  to  enter,  thoroughly 


dried  by  its  passage  over  the  chlorid  of  calcium.  It  is  again 
exhausted,  and  this  process  repeated  four  or  five  times,  by 
which  the  mixture  is  completely  dried.  The  annexed  figure 
shows  the  arrangement  for  this  purpose. 

686.  The  tube  is  now  ready  for  the  combustion,  and   is 
placed    in    the 
furnace    repr 
sented     in    tl 
accompanying 
figure.       It    is 

constructed  of  sheet  iron,  and  fitted  with  a  series  of  sup- 
porters at  short  distances  from  each  other,  to  prevent  the  tube 
from  bending  when  softened  by  heat.  The  furnace  is 
placed  on  a  flat  stone  or  tile,  with  the  front  slightly  inclined 
downwards.  The  quantity  of  water  formed  in  the  process 
is  estimated  by  a  light  tube,  represented  in  the  annexed 
figure,  which  is  filled  with  ^__-nt, tfjuMupM^ii  i  ajjISLL— — 

calcium,  and  after  having  been  very  carefully  weighed,  is 
attached  by  a  well  dried  and  closely  fitting  cork,  to  the  end 
of  the  combustion  tube.  To  determine  the  carbonic  acid, 
a  small  five-bulbed  tube  of  peculiar  form,  called  Liebig's 


360  ORGANIC    CHEMISTRY. 

potash  bulb,  and  represented  in  the  annexed 
figure,  is  used.  It  is  charged  for  this  pur- 
pose with  a  solution  of  caustic  potash  of  a 
specific  gravity  about  1-25,  with  which  the 
three  lower  bulbs  are  nearly  filled.  Its  weight 
is  determined  with  great  exactness,  and  it  is 
then  attached  to  the  chlorid  of  calcium  tube, 
by  a  little  tube  of  gum  elastic,  which  is  held 
fast  by  a  silken  cord.  The  whole  arrange- 
ment is  shown  below.  The  tightness  of  the  junction  is  as- 
certained by  drawing  a  few  bubbles  of  air  through  the  end 


of  the  potash  tube,  so  that  the  liquid  will  be  raised  a  few 
inches  above  the  level  on  the  other  side  ;  if  this  level  remains 
the  same  for  some  minutes,  the  whole  apparatus  is  tight. 

687.  Heat  is  now  applied  by  means  of  ignited  charcoal 
placed  around  the   anterior   portion  of  the  tube,  and  when 
this  is  red-hot,  the  fire  is  gradually  extended  along  the  tube, 
by  means  of  a  moveable  screen,  represented  in  the  figure. 
This  must  be  done  so  slowly  as  to  keep  a  moderate  and  uni- 
form   flow  of  gas  through  the  potash  solution.     When   the 
whole  tube  is  ignited,  and  gas  no  longer  escapes,  the  closed 
end  of  the  combustion  tube  is  broken   off,  and   a  little  air 
drawn  through  the  apparatus  to  remove  all  the  remaining 
products  of  combustion.     The  tubes  are  then  detached,  and 
from  the  increase  of  weight  in  the  chlorid  of  calcium  tube, 
the  amount  of  water,  and  hence  that  of  hydrogen,  is  deduced. 
The  carbon  is  determined  from  the  increase  in  weight  of  the 
potash  bulbs,  by  a  simple  calculation. 

688.  Volatile  fluids  are  analyzed  by  enclosing  them  in  a 
narrow-necked  bulb  of  thin  glass,  filled  with  the  fluid  in  the 
same    mode   as    thermometers,    (76.)     The    weight   of  the 
empty  tube  is  first  ascertained ;  the  fluid  is  introduced,  the 
neck   sealed,  the  weight  being  again    ascertained,   and  the 


ANALYSIS   OF    ORGANIC    SUBSTANCES.  361 

difference  gives  the  weight  of  the  fluid. 
The  neck  of  the  bulb  is  then  broken 
by  a  file  mark  at  a,  dropped  into  the 
closed  end  of  the  combustion  tube,  and 
covered  with  oxyd  of  copper,  which 
should  nearly  fill  the  tube.  When  this 
is  heated  to  redness,  a  gentle  heat  ap- 
plied to  the  portion  of  the  combustion  ( 
tube  containing  the  volatile  fluid,  sends 
it  in  vapor  over  the  ignited  oxyd,  completely  burning  it.  The 
products  of  its  combustion  are  estimated  as  before. 

689.  Fatty  bodies  and  others  which  contain  much  car- 
bon and  a  small  quantity  of  hydrogen,  are  more  perfectly 
burned  by  employing  chromate  of  lead  in  place  of  the  oxyd 
of  copper.     This  substance  does  not  readily  attract  moisture 
from  the  atmosphere,  like  oxyd  of  copper,  and  is  consequently 
better  when   the  hydrogen  is  to    be  determined  accurately. 
The  chromate  of  lead  (595)  is  prepared  for  use  by  heating 
it  until  it  begins  to  fuse,  and  when  cool  reducing  it  to  powder. 

690.  When  nitrogen  is  a  constituent  of  organic  bodies, 
it  is  determined  by  placing  in   one   end  of  the  combustion 
tube,  about  three  inches  of  carbonate  of  copper,  secured  in 
its  place  by  a  plug  of  asbestus ;  and  then  the  nitrogenous 
body  is  introduced,  mixed  with  oxyd  of  copper.      The  re- 
maining space  in  the  combustion  tube  is  filled  with  turnings 
of  metallic  copper.     The  air  is  then  withdrawn   by  an  air- 
pump,  and  a  gentle  heat  applied   to  the  carbonate  of  copper, 
which   evolves  carbonic  acid,  and  drives  out  all   remaining 
traces  of  common  air.     The  tube  is  now  heated  as  usual, 
and  the  gases  evolved  are  collected  in  a  graduated  air-jar, 
over  mercury.     When    the   combustion  is  finished,  heat  is 
again  applied  to  the  carbonate  of  copper,  and  another  portion 
of  carbonic  acid  expelled,  which   drives  out  all  the  nitrogen 
from  the  tube.     The  use  of  the  copper  turnings  is  to  decom- 
pose any  traces  of  nitric  oxyd,  which  may  be  formed  in  the 
process.     The  carbonic  acid  is  removed  from  the  air-jar,  by 
a   strong   solution   of  potash,  and   pure   nitrogen    remains, 
which  is  measured  with   the  usual   precautions,  and  from  its 
volume  the  weight  is  easily  determined. 

691.  Another  and  a  preferable  mode  of  determining  nitro- 
gen, is  that  of  Will  and  Varrentrapp,  which   is  founded  on 
fhe  fact  that  when  a  body  containing  nitrogen  is  heated  with 
an   excess   of  caustic  potash,  or  soda,  all    the   nitrogen  is 

31 


362  ORGANIC    CHEMISTRY. 

evolved  in  the  form  of  ammonia,  and  may  be  thus  estimated, 
by  conducting  it  into  hydrochloric  acid. 

692.  Chlorine  is  determined  in  the  analysis  of  organic 
compounds,  by  passing  the  vapor  over  quick  lime  heated  to 
redness  in  a  combustion  tube;  chlorid  of  calcium  is  formed, 
which  is  afterwards  dissolved  in  water,  and  the  chlorine  pre- 
cipitated by  nitrate  of  silver.     From  the  weight  of  the  chlorid 
of  silver,  the  amount  of  chlorine  is  calculated. 

693.  Sulphur  is  a  rare  constituent  of  organic  compounds. 
Its  presence  is  detected  by  fusion  with  nitre  and  carbonate  of 
soda,  or  by  digestion  with  nitric  acid.     Sulphuric  acid  is  thus 
formed,  and   is   precipitated   as  sulphate  of  baryta,  from  the 
weight  of  which,  that  of  the  sulphur  is  determined.     In  the 
analysis  with  oxyd  of  copper,  a  small   tube  of  peroxyd  of 
lead  is  introduced  between   the  chlorid  of  calcium   tube  and 
the  potash  apparatus,  to  absorb  the  sulphurous  acid  which  is 
evolved. 


ORGANIC  COMPOUNDS  AND  PRODUCTS  OF  THEIR 
ALTERATION. 

AMMONIA,    NH3. 

694.  The  properties  of  ammonia  and  of  its  salts  have  been 
already  described,  (43S.)     It  is  a  constant  product  of  the 
decomposition  of  all  organic  matters  which  contain  nitrogen ; 
and  carbonate  of  ammonia    is  obtained  in    large  quantities 
in    the   dry  distillation  of  horns,  bones,  and    other  animal 
substances.  When  any  nitrogenous  organic  substance  is  heated 
with  an  excess  of  hydrate  of  potash,  its  carbon  is  oxydized 
by  the  oxygen  of  the  water,  and   all   the  nitrogen  combining 
with  the  hydrogen  is  evolved  in  the  form  of  ammonia. 

695.  An    equivalent    substitution    (438)    of    chlorine, 
bromine,  or  iodine,  may  be  made  for  the  hydrogen  of  ammo- 
nia, as  in  the  production  of  interesting  compounds.     Thus 
when  a  jar  of  chlorine  is  inverted  in  a  solution  of  an  ammo- 
niacal  salt,  the  gas  is  absorbed  and  a  heavy  yellow  oily  fluid 
separates,   which  is  known  as  chlorid  of  nitrogen,  NC13 : 
it  is  formed  from  ammonia  by  the  substitution  of  chlorine  for  its 
hydrogen.     This  is  a  most  explosive  and  dangerous  body. 
Even  a  gentle  heat,  the  contact  of  phosphorus,  fat  oils,  and  many 
other  agents,  cause  it  to  be  decomposed  with  a  very  violent 
explosion.     Bromine  forms  an  analogous  compound,  (NBr3.) 


AMMONIA.  363 

The  reaction  of  ammonia  with  iodine,  (when  these  two  sub- 
stances are  triturated  together,)  produces  a  compound  in 
which  two  of  its  equivalents  of  hydrogen  are  replaced  by 
iodine,  giving  us  the  formula,  NI2H.  It  is  a  heavy  black 
powder,  which  can  hardly  be  dried  from  the  ammoniacal 
liquor,  without  explosion,  and  which  the  slightest  friction  causes 
to  be  decomposed  with  a  violent  detonation.  These  bodies 
may  be  called  tri-chlorinized  and  bin-iodized  ammonia. 

Potassium  when  heated  in  dry  ammonia  displaces  one 
equivalent  of  hydrogen,  forming  NH2K.  This  is  an  olive- 
green  mass,  which  is  resolved  by  water  into  ammonia  and 
potash,  NH2K  +  HO==NH3KO. 

696.  Ammonia   is    largely    absorbed    by   many    metallic 
salts,  and  forms  with  them  definite  crystalline  compounds ; 
for  example,  the  salts  of  silver,  copper,  and  zinc  combine 
with  two  equivalents    of  ammonia:    but  the  affinity  which 
holds  the  ammonia  is  feeble,  and  it  may  be  often  expelled 
from  these  combinations  by  a  gentle  heat.     In  some  instances, 
however,  the  action  is  different ;  thus  when  ammonia  is  added 
to  a  solution   of  chlorid   of  mercury,  a  white   precipitate  is 
formed,  which   appears   to   be   a  compound  of   HgCl  with 
NH2Hg,    corresponding   to    the    potassium    compound    just 
described,  HgCl  +  NH3  =  NH2Hg  +  HC1.     The  hydrochloric 
acid  combines  with  another  portion  of  ammonia  to  form  sal- 
ammoniac.     When  a  solution   of  ammonia   is  digested  with 
calomel  (HgaCl)  a  black  powder  is  formed,  the  composition 
of  which  may  be  represented  by  Hg2Cl  -f  NH2Hg2.     This 
reaction  is  like  the  last ;  the  chlorine  unites  with  one  equiva- 
lent of   hydrogen,   which   is   replaced  by  the  residue  Hg2. 
These  are  examples  of  the  substitution  by  residues,  (675.) 

697.  Amides. — The  action  of  ammonia  upon  many  orga- 
nic substances  containing  oxygen  is  peculiar ;  one,  two,  or 
three  of  its  equivalents  of  hydrogen  combine  with  the  oxygen 
of  the  organic  body,  and  the  residues  unite.     Compounds  are 
thus  produced  in  which  NH2,  NH,  or  N  replace  the  whole  or 
a  part  of  the  oxygen  of  the  organic  compound.     To  these  the 
name  of  amides  has  been  given.     Neither  ammonia  nor  the 
organic  matter  can  be  detected  in  such  compounds  by  the 
usual  tests,  but  by  the  aid  of  acids  and  heat  they  take  up  the 
elements  of  water  and  reproduce  the  original  substances ;  the 
ammonia  combining  with  the  acid,  while  the  organic  body  is 
set  free.     When  the  organic  substance  forming  the  amide  is 
an  acid,  a  similar  change  is  effected   by  a  solution  of  an 


364 


ORGANIC    CHEMISTRY. 


alkali ;  the  regenerated  acid  forms  a  salt  with  the  alkali,  and 
ammonia  escapes. 

698.  The  amides  of  monobasic  acids  are  derived  from  one 
equivalent  of  the  acid  and  one  of  ammonia,  by  the  loss  of 
two  equivalents  of  water.  The  bibasic  acids  afford  two 
amides  corresponding  to  their  neutral  and  acid  salts.  (674.) 
These  may  often  be  formed  by  the  action  of  heat  upon  the 
ammoniacal  salts,  which  are  resolved  into  water  and  an 
amide.  Thus  the  oxalate  of  ammonia,  when  heated,  loses 
four  equivalents  of  water  and  is  converted  into  oxamide,  C4H2 
O8  -f  2NH3  (oxalate  of  ammonia)  =  4HO  -f  C4H4N?O4.  This 
is  a  neutral  insoluble  body,  which  is  converted  into  oxalic 
acid  and  ammonia  by  solutions  of  both  alkalies  and  acids. 
The  acid  oxalate  of  ammonia,  C4H2O8  +  NH3,  loses  in  the 
same  manner  two  equivalents  of  water  and  yields  oxamic 
acid,  C4H3NO6.  This  is  a  monobasic  acid,  and  yields  a  series 
of  salts ;  it  is,  however,  a  proper  amide,  and  is  decomposed 
by  the  same  agents  as  oxamide.  When  boiled  for  some  time 
with  water  it  takes  up  the  elements  of  two  equivalents,  and  is 
converted  into  acid  oxalate  of  ammonia. 


THE  GROUP  OF  ALCOHOLS  AND  THE  PRODUCTS  OF 
THEIR  ALTERATION. 

ALCOHOL,    C4H6O2. 

699.  This  important  substance  is  a  product  of  the  fermen- 
tation of  sugar,  and  is  contained  in  all  fermented  liquors. 


ALCOHOL.  365 

From  these  it  is  obtained  by  distillation.  A  convenient  appa- 
ratus for  condensing  the  vapor  of  alcohol,  ether,  and  other 
volatile  products  of  distillation,  is  represented  in  the  foregoing 
figure.  The  general  arrangement  is  similar  to  the  usual  dis- 
tillatory apparatus,  (117.)  The  neck  of  the  retort  passes 
into  a  large  glass  tube,  which  is  encased  by  an  outer  one  of 
metal  closely  adapted  by  corks  at  its  ends  to  the  glass  tube, 
leaving  a  water-tight  cavity  between  the  two,  which  is  filled 
with  cold  water  by  a  tube  entering  near  the  lower  end  and 
terminating  in  a  funnel  at  a  higher  level,  where  water  is  sup- 
plied from  a  small  tank  with  a  cock.  An  orifice  near  the 
upper  end  of  the  condenser  permits  the  water  to  escape  when 
it  has  risen  to  a  higher  level  in  the  upper  tube.  This  arrange- 
ment, (called  from  its  inventor  a  "  Liebig's  condenser")  secures 
an  uninterrupted  flow  of  cold  water  into  the  condenser 
as  fast  as  the  heated  water  escapes  from  the  upper  end,  and 
the  most  volatile  vapors  are  easily  condensed  to  fluids  in  such 
an  apparatus.  If  necessary,  iced  water  can  be  employed. 
Alcohol  thus  distilled,  still  retains  fifteen  per  centum  of  water. 
This  is  removed  by  digestion  with  quick  lime  or  chlorid  of 
calcium,  which  appropriate  the  water,  and  another  distillation 
yields  anhydrous  or  absolute  alcohol. 

700.  Pure  alcohol  is  a  colorless  fluid,  with  a  specific  gra- 
vity of  *795,  and  boils  at  173°  F.  It  has  a  pungent  and 
agreeable  taste,  and  a  fragrant  odor.  It  is  very  combustible, 
and  burns  with  a  pale  blue  flame  without  smoke,  which  ren- 
ders it  very  useful  as  a  source  of  heat  in  chemical  processes. 
The  action  of  alcohol  on  the  system,  is  well  known  as  that  of 
a  powerful  and  dangerous  stimulant.  It  is  largely  used  in 
the  operations  of  the  arts,  the  preparation  of  medicines,  and 
the  processes  of  chemistry.  Its  solvent  powers  are  very 
great ;  the  volatile  oils  and  resins  are  dissolved  by  it,  as  well 
as  many  acids  and  salts,  the  caustic  alkalies,  and  a  large 
number  of  other  substances. 

The  specific  gravity  of  the  vapor  of  alcohol  is  1600,  air 
being  1 000  ;  and  its  equivalent  is  represented  by  four  vol- 
umes, oxygen  being  one.  It  is  composed  of 

4  volumes  of  carbon  vapor,      4  X      '832     =     3-3280 

12         "  hydrogen,  12  X    -0693     =       -8316 

2         «  oxygen,  2  X  1-1093     =     2-2186 

Equal  to  four  volumes  of  alcohol  vapor,  6-3782 

Of  which  one  volume  weighs,  1-5946 

31* 


366  ORGANIC    CHEMISTRY. 

701.  Sulphur  Alcohol,  Mercaptan,  C4HCS2. — This  singu- 
lar compound  is  alcohol  in  which  sulphur  replaces  the  oxygen. 
It  is  a  colorless  and  very  volatile  fluid,  and  has  a  very  pow- 
erful odor,  resembling  onions.     It  acts  upon  oxyd  of  mercury 
with  great  violence  ;*  water  is  formed,  and  a  white  crystal- 
line substance,  which  is  C4H5IIgS2.     Analogous  compounds 
may  be  obtained  by  its  means  with  other  metallic  oxyds,  and 
the  term    mercaptides  has    been    used    to  distinguish  them. 
Mercaptan  is  a  fine  example  of  the  equivalent  substitution  of 
sulphur  for  oxygen  in  organic  compounds.     Mercaptan  may 
be  procured  by  saturating  a  solution  of  caustic  potash,  (den- 
sity of  1-3,)  with  sulphureted  hydrogen  gas,  arrd  distilling 
this   in    a  retort  with  an  equal  volume  of  sulphovinate  of 
time  of  the  same  density.     The   regulated   temperature  of  a 
salt  bath,  and   a  Liebig's  condenser  are  necessary,  and  the 
mercaptan  is  separated  by  a   funnel   from  the  accompanying 
water,  which  collects  with  it  in  the  cold  condenser. 

Action  of  Acids  upon  Alcohol. 

702.  Ethers. — The  action  of  acids  upon  alcohol  is  highly 
important  in  relation  to  chemical  theory,  and  has  been  very 
attentively  studied.    When  a  monobasic  acid  acts  upon  alcohol 
a  combination  takes  place,  with  the  elimination  of  two  equiva- 
lents of  water.     The  resulting  compounds  are  called  ethers, 
and  have  been  considered  as  stilts,  in  the  formation  of  which 
alcohol  minus  one  equivalent  of  water  plays  the  part  of  a 
metallic  oxyd.       Unlike  saline  combinations,  however,  the 
acids  of  the  ethers  cannot  be  recognised  by  the  usual  tests: 
for  example,  oxalic  ether  does  not  produce  any  precipitate  in 
the  solutions  of  a  salt  of  lime,  while  all  the  oxalates  precipi- 
tate   lime   from   its   solutions  as   insoluble   oxalate.     When 
heated  with  the  solution  of  a  fixed  alkali,  the  ethers  take  up 
the  elements  of  two  equivalents  of  water,  regenerating  alcohol 
and  the  acid.     This  change  is  sometimes  effected  by  boiling 
with  water. 

703.  A  bibasic  acid  reacts  in  the  same  manner  with  two 
equivalents  of  alcohol  and  the  separation  of  four  equivalents 
of  water.     Thus  oxalic  acid,  C4H2O8,  and  two  of  alcohol, 
2C4H6O2,  yield  one  equivalent  of  oxalic  ether  and  four  of 
water,  C,2H10O8+4HO.     Often,  however,  the  reaction  is  dif- 
ferent; an  equivalent  of  the  acid  acts  upon  but  one  equivalent 

*  Whence  its  name,  Mercy-riitm  eapt ans. 


ALCOHOL.  367 

of  alcohol,  and  produces  an  acid  ether  which  is  capable  of 
neutralizing  bases  to  form  salts.  These  are  called  vinic 
acids,  and  are  monobasic  ;  e.  g.  oxalovinic  and  sulphovinic 
acids.  If  we  represent  the  residue  C4H6O2  —  H2  by  E,  the 
composition  of  these  compounds  may  be  represented  thus  — 

Oxalic  acid,  C4H208 

Oxalic  ether,          C4H2  * 


Oxalovinic  acid,     C4H2     -j  °,6 


In  these  compounds  the  residue  represented  by  E  replaces 
two  equivalents  of  oxygen. 

704.  Tribasic  acids  in  the  same  way  form   neutral  ethers 
with  three  equivalents  of  alcohol,  or  bibasic  acids,  with  one 
equivalent.     The  power  of  forming  vinic  acids  or  acid  ethers 
with  alcohol,  belongs  only  to  those  acids  which  are  polybasic  ; 
and  the  study  of  these  reactions  has  shown  us  that  several 
acids   usually  considered   as    monobasic  are  really   bibasic 
acids.     Thus  the  sulphuric  yields  with  alcohol  sulphovinic 
acid  with  wood-spirit,  (a  compound  closely  allied  to  alcohol 
in  its  chemical  relations,)  a  corresponding  acid,  and  a  neutral 
ether.     Agreeably  to  this  view  the  formula  of  sulphuric  acid 
must  be  doubled—  thus  S2H2O8=  2SHO4,  or  2SO3HO.     It  will 
be  remembered  that  this  acid  forms  both  neutral  and  acid 
salts,  as  well  as  salts  with  two  fixed  bases,  and  is  for  this 
reason  also  to  be  considered  bibasic,  (674.)     Carbonic  acid 
is  in  the  same  way  bibasic,  since  it  forms  neutral  and  acid 
carbonates,  and  yields  with  alcohol  carbonic  ether,  and  car- 
bovinic  acid.     Nitric  acid  on  the  other  hand  yields  a  neutral 
ether  with  one  equivalent  of  alcohol  ;  it  never  forms  acid  or 
double  salts,  and  is  an  example  of  a  monobasic  acid. 

The  vinic  acids  and  those  formed  in  a  similar  manner  are 
conveniently  designated  as  coupled  acids. 

705.  In  these  coupled  acids,  as  in  the  neutral  ethers,  the 
original  acid  cannot  be  detected  by  the  usual  tests.     The  sul- 
phovinate  of  baryta  is  a  very  soluble  salt,  while  the  sulphate 
of  the   same  base  is  a  very  insoluble   compound.     When 
heated  with  hydrate  of  potash,  the  sulphovinates  assume  the 
elements  of  water,  and  regenerate  the  acid  and  alcohol. 

It  will  be  observed  that  the  ethers  present  many  analogies 
to  the  amides  in  formation  and  composition,  as  well  as  in  the 
mode  of  their  decomposition  by  alkalies.  The  similarity  of 
origin  will  be  seen  by  comparing  the  oxalic  ether  arid  amides 


368  ORGANIC    CHEMISTRY. 


Oxamide,  C4H2N2O4  = 

Oxalic  ether,  C,2H10O8  C4H2O8  +  20,1^02—  4HO 

Oxamicacid,  C3H3N06  C4H2O8  +  NH3—  2  HO 

Oxalovinijc  acid,  CgHeOg  =          C4H2O8  +  C4H6O2—  2HO 


The  neutral  ether  and  amide  are  derived  from  one  equiva- 
lent of  the  acid,  and  two  of  ammonia  or  alcohol,  by  the  loss 
of  four  equivalents  of  water ;  and  the  oxamic  and  oxalovinic 
acids,  which  are  monobasic,  are  in  like  manner  formed  from 
an  equivalent  of  the  bibasic  acid  and  one  of  ammonia  or 
alcohol,  by  the  abstraction  of  two  of  water. 

706.  Nitric  Ether,  C4H5N06. — This  compound  is  formed 
by   distilling  equal   parts  of  strong  nitric  acid  and  alcohol 
with  a  few  grains  of  urea.     The  action  of  nitric  acid  upon 
alcohol   is   very  violent.     Nitrous  acid  is  formed,  which  de- 
composes the  ether,  and  gives  rise  to  a  variety  of  products ; 
but  a   little  urea  prevents  this,  and  the  distillation  proceeds 
quietly,  yielding  nitric  ether  and  water,  C4H6O2  +  NHO6r= 
2HO  -\-  C4H5NO6.     It  is  a  colorless  liquid  of  a  very  sweet 
taste,  is  insoluble  in  water,  has  a  specific  gravity  of  1*1 12, 
and    boils   at    185°    F.     The   vapor   explodes    by    a    mod- 
erate heat.     When  this  ether  is  mixed  with  a  solution   of 
potash  in  dilute  alcohol,  it  reassumes  the  elements  of  water, 
and  yields  alcohol  and  nitrate  of  potash. 

707.  Perchloric  Ether,  C4HCI6. — This   is   an  extremely 
explosive  compound,  which  is  produced  from  the  distillation  of 
a  concentrated  solution  of  perchlorate  and  sulphovinate  of 
barytes,  in  equivalent  proportions.     So  long  as  the  salts  re- 
main   in    solution  no  reaction  occurs,  but  as  soon  as  they 
become  solid  a  reciprocal  decomposition  ensues,  and  a  sweet 
ethereal  liquid  collects  in  the  receiver.     This  is  the  compound 
which  has  been  called  perchloric  ether  by  Messrs.  Hare  and 
Boye.*    It  is  a  transparent  colorless  liquid,  heavier  than  water, 
with  a  pungent  agreeable  smell,  and  very  sweet  taste,  which 
leaves  a  biting  impression  on  the  tongue,  similar  to  that  of 
oil  of  cinnamon.     It  explodes  by  ignition,  friction,  or  percus- 
sion, sometimes  with  no  assignable  cause,  and  with  such  pecu- 
liar violence  that  the  smallest  drop  of  it,  when  exploded  upon 
an  open  porcelain  plate,  will  shatter  it  into  fragments.     It  is 
unsafe  to  operate  with  it  unless  protected  by  gloves  and  a  close 
mask  with  thick  glass  eye-holes,  and  with  the  intervention  of 
a  moveable  wooden  screen.     It  dissolves  in  alcohol,  and  an 

*American  Journal  of  Science,  (1st  Series,)  vol.  42,  p.  62. 


ALCOHOL.  369 

alcoholic  solution  of  potash  added  to  the  solution  of  the 
ether  in  alcohol  decomposes  it,  with  the  production  of  in- 
soluble perchlorate  of  potash. 

708.  Hydrochloric  Ether,  C4H5CI.  —  This  substance  is 
obtained  by  saturating  alcohol  with  hydrochloric  acid  gas,  when 
the  ether  passes  over,  and   must  be  condensed  by  a  freezing 
mixture,   C4HCO2  +  HC1=C4H5C1  +  2HO.     It  is  a  colorless, 
very  volatile  liquid,  with  a  pungent  aromatic  odor,  and  is 
slightly  soluble  in  water.     It  has  a  specific  gravity  of  -873, 
and  boils  at  52°  F.     With  a  solution  of  potash  it  is  decom- 
posed like  all  the  other  ethers,  and  yields  chlorid  of  potassium 
and  alcohol. 

709.  Hydrobromic  Ether,  C4H5Br. — When  a  mixture  of 
alcohol,  bromine,  and  phosphorus  is  distilled,  hydrobromic 
acid  is  formed,  which  reacts  with  the  alcohol  to  form  hydro- 
bromic ether.     It  is  a  volatile  fluid,  heavier  than  water,  and 
closely  resembles  the  hydrochloric  ether. 

Hydriodic  Ether,  C4H5I,  is  obtained  by  substituting  iodine 
for  bromine  in  the  last  process.  It  is  a  colorless  liquid,  of 
specific  gravity  1-92,  and  boils  at  160°. 

710.  Acetene,  C4H6. — When  hydrochloric  ether  is  decom- 
posed by  potassium,  chlorid  of  potassium   is  formed,  and  a 
white   crystalline   compound,    which     is    C4H5K.  "    This   is 
decomposed  by  water,  into  water  and   a  volatile  oily  liquid, 
which  is  C4H6.     To  this  the  name  of  acetene  is  given.     The 
bodies  formed   by  the  action  of  hydrochloric,  hydrobromic, 
and  hydriodic  acids  upon  alcohol,  and  which  have  just  been 
described  as  ethers,  may  be  viewed  as  acetene,  in  which  an 
equivalent  of  hydrogen  is  replaced   by  chlorine,  bromine,  or 
iodine.     A  peculiar  compound  formed  by  the  action  of  nitric 
or  nitrous  acid  upon  alcohol,  may  be  viewed  as  a  derivative 
of  acetene. 

Nitric  Acetene;  Nitrous  Ether;  Hyponitric  Ether, 
C4H5NO4. — The  red  vapors  evolved  by  the  action  of  nitric 
acid  upon  starch,  are  rapidly  absorbed  by  dilute  alcohol, 
with  the  evolution  of  heat,  and  the  present  compound  passes 
off  in  vapor  and  may  be  condensed.  It  is  a  pale  yellow 
fluid,  of  a  very  fragrant  odor  of  apples ;  it  has  a  specific 
gravity  of  -947,  and  boils  at  62°.  This  substance  is  re- 
garded by  many  as  the  ether  of  hyponitric  acid,  but  it 
does  not  appear  to  yield  alcohol  and  a  hyponitrate  by  the 
action  of  potash,  as  it  should  do  if  it  were  like  the  ethers. 
It  results  from  the  action  of  NO3+C4HeO2=:HO-f  C4H5NO4i 


370  ORGANIC    CHEMISTRY. 

and  may  oe  regarded  as  derived  from  acetene  and  nitric 
acid,  by  the  abstraction  of  2HO.  This  substance  is  formed 
among  many  others,  when  alcohol  is  acted  on  by  nitric  acid, 
and  an  alcoholic  solution  of  the  impure  product  constitutes  the 
sweet  spirits  of  nitre,  used  in  medicine.  It  was  formerly 
obtained  by  distilling  a  mixture  of  nitre  with  sulphuric  acid 
and  alcohol. 

711.  Sulphovinic  Acid,  C4H6S2O8. — The  proper  sulphu- 
ric  ether,    with    two    equivalents  of  alcohol,  has    not  been 
obtained.     When   equal  weights    of  alcohol    and  sulphuric 
acid    are   mixed   and  heated  to  boiling,  sulphovinic  acid   is 
formed,  and  remains  in  the  fluid  ;  the  mixture  is  allowed  to 
cool,  diluted  with  water,  and  neutralized  with  chalk.     The 
excess  of  sulphuric  acid  forms  an  insoluble  sulphate  with  the 
lime,  while  the  soluble  sulphovinate  of  lime  remains  in  solu- 
tion, and  is  obtained  in  crystals  by  evaporation  and  cooling. 
It  forms  beautiful  colorless  prisms,  which   have  the  composi- 
tion  C4H5CaS2Op  -f  2aq ;    they    lose   the    water   in   a    dry 
atmosphere.     The  sulphovinate  of  potash  is  obtained  by  de- 
composing the  lime  salt  with  carbonate  of  potash. 

If  carbonate  of  baryta  is  substituted  for  chalk  in  neutral- 
izing the  acid  mother-liquor,  sulphovinate  of  baryta  may 
be  obtained  in  fine  crystals.  From  a  solution  of  this  salt, 
dilute  sulphuric  acid  precipitates  all  the  baryta,  and  a  solution 
of  sulphovinic  acid  is  obtained,  which  may  be  concentrated 
in  vacuo.  It  forms  a  sour  syrupy  liquid,  which  is  decom- 
posed by  a  gentle  heat,  (or  even  by  too  much  concentration,) 
into  alcohol  and  sulphuric  acid. 

712.  Sulphovinic  acid  is  derived  from  one  equivalent  of 
sulphuric  acid,  and  one  of  alcohol,  by  the  abstraction  of  the 
elements  of  two  equivalents  of  water,   S2H2O8  +  C4H6O2  = 
C4H6S2O8  +  2HO,  and  in  its  decomposition  it  reassumes  the 
2HO.     When  a  sulphovinate  is  distilled  with  hydrate  of  pot- 
ash, it  yields  alcohol  and  a  sulphate  of  potash;  if,  in  place  of 
hydrate  of  potash,  the  hydrosulphuret  is  employed,  sulphur 
alcohol  is  obtained;    C4H6S2O8  +  KSHS  =  C4H6S2  +  S2HK08. 
(701.)     When  a  sulphovinate  is  distilled  with  any  salt,  as  ace- 
tate of  lime,  a  double  exchange  ensues ;  the  acetic  acid  takes 
the  place  of  sulphuric  and  forms  acetic  ether,  while  sulphate 
of  lime  remains. 

713.  Carbovinic  Acid. — When  carbonic  acid  acts  upon 
a  solution  of  potash  in  absolute   alcohol,   crystals   of  car- 
bovinate  of  potash  are  formed ;  they  have  the  composition 


ALCOHOL.  371 

C6H5KO6.  This  acid  cannot  be  isolated.  The  carbonic 
-ether  is  formed  by  the  action  of  potassium  upon  oxalic  ether. 
It  is  a  colorless  liquid,  which  contains  C]0HJOO6,  and  by  the 
action  of  potash  takes  up  the  elements  of  water,  and  yields 
alcohol  and  carbonate  of  potash. 

By  the  action  of  sulphuret  of  carbon  upon  an  alcoholic 
solution  of  potash  we  obtain  sulphurized  carbovinate  of  potash, 
in  which  sulphuret  of  carbon  acts  the  part  of  carbonic 
acid.  The  acid  is  an  oily  liquid,  of  a  sour  and  bitter  tasle ; 
its  formula  is  CgH^OgS^ =carbovmic  acid,  C6H6O6,  in  which 
four  equivalents  of  oxygen  are  replaced  by  sulphur.  From 
the  yellow  color  of  some  of  its  salts  it  was  originally  de- 
scribed under  the  name  of  xanthic  acid. 

Phosphovinic  acid  is  formed  by  the  reaction  of  one  equiva- 
lent of  tribasic  phosphoric  acid  and  one  of  alcohol.  It  is  a 
bibasic  acid,  and  in  its  general  characters  resembles  sulpho- 
vinic  acid.  Arsenic  acid  forms  an  allied  compound,  the 
arsenovinic  acid. 

714.  Silicic  Ethers. — Two  ethereal  compounds  are  formed 
by  the  reaction  of  chlorid  of  silicon  upon  alcohol.     They  are 
odorant  and  volatile  liquids,  of  a  pungent  taste ;  one  has  the 
formula  C12Hi5SiOfi,  and  contains  the  elements  of  one  equiva- 
lent of  silicic  acid  and  three  of  alcohol,  minus  the  elements 
of  water.     The  formula  C4H5Si2O7  is  ascribed  to  the  other, 
and    both  of  them   are   slowly  decomposed    by  water,  and 
rapidly  by  alkalies  into  alcohol  and  silicic  acid.     When  ex- 
posed  to  moist  air  in  vessels  partially  closed,  they  deposit 
silicic  acid  in  beautiful  transparent  masses,  resembling  the 
finest  rock-crystal.     By  the  action  of  the  chlorid  of  boron 
upon    alcohol,  two   boracic   ethers  are  produced  similar  in 
composition  and  properties  to  the  last :  they  burn  with  a  fine 
green  flame,  which  is  characteristic  of  the  combustion  of  an 
alcoholic  solution  of  boracic  acid — boracic  ether  being  formed 
by  this  combustion,  and  in  the  distillation  of  alcohol  with 
boracic  acid.  (370.) 

Products  of  the  decomposition  of  Sulphovinic  Acid. 

715.  Ether. — When  dilute  sulphovinic  acid  is  heated  to 
boiling,  it  is  decomposed  into  sulphuric  acid  and  alcohol,  but 
when  a  mixture  of  equal  weight  of  sulphuric  acid  and  alcohol 
is  boiled,  water  is  evolved,  and  a  liquid  which  may  be  repre- 
sented as  C4H5O.     In  the  first  of  these  cases,  the  sulphovinic 
acid  takes  up  the  elements  of  two  equivalents  of  water,  and 


372 


ORGANIC    CHEMISTRY. 


regenerates  alcohol  and  the  acid  ;  but  in  the  second,  this 
acid,  when  decomposed  at  the  boiling-point  of  the  liquid, 
about  300°  F.,  assumes  the  elements  of  but  one  equivalent  of 
•water,  and  evolves  the  new  compound  ether.  The  best  pro- 
portions for  preparing  this  ether,  are  five  parts  of  alcohol  of  90 
percent.,  and  eight  of  ordinary  sulphuric 
acid.  The  mixture  is  placed  in  a  flask, 
(a,)  through  the  cork  of  which  is  intro- 
duced a  thermometer  (d)  and  two  tubes, 
one  of  which  (c)  conveys  away  the 
vapors  to  a  condenser,  and  the  other 
(b)  is  connected  with  a  reservoir  of 
alcohol.  The  mixture  is  heated  to  the 
boiling-point  (about  300°  F.)  and  care- 
fully maintained  at  that  temperature. 
Alcohol  is  now  admitted  through  the 
tube  6,  in  a  quantity  sufficient  to  pre- 
serve the  original  level  of  the  liquid  in 
the  retort,  the  supply  being  regulated 
by  a  stopcock.  During  the  whole  ope- 
ration the  liquid  must  be  kept  violently 
boiling,  and  the  alcohol  is  then  com- 
pletely decomposed  into  ether  and  water, 
which  distil  over  together,  and  condense 
in  the  receiver.  With  these  precautions 
the  process  may  be  carried  on  for  a 
long  time,  the  only  limit  to  it  being, 
that  the  acid  is  slowly  volatilized,  in 
combination  with  a  portion  of  the  alcohol.  The  ether  which 
floats  on  the  water  in  the  receiver,  is  separated,  and  purified 
by  distilling  with  a  little  caustic  potash. 

This  reaction  is  explained,  by  the  fact  that  sulphovinic  acid 
is  formed  when  the  mixture  is  heated  to  285°,  and  decomposed 
at  a  temperature  a  few  degrees  above  it,  if  the  liquid  is  boiling. 
The  alcohol,  as  it  flows  into  the  boiling  mixture  through 
the  tube  6,  reduces  the  temperature  at  the  point  of  contact, 
so  that  sulphovinic  acid  is  formed,  and  a  portion  of  the  water 
elininated  is  immediately  volatilized.  As  soon  as  the  newly 
formed  acid  mixes  with  the  boiling  liquid,  it  is  decomposed 
and  ether  is  evolved.  The  result  is,  that  with  each  equiva- 
lent of  ether,  one  of  water  is  volatilized — so  that,  in  effect, 
the  alcohol  is  resolved  into  these  substances. 

This  body  is  the  sulphuric  ether  of  commerce,  and  so 


ALCOHOL.  373 

well  known  in  medicine.  But  it  should  be  carefully  distin- 
guished from  those  compounds,  which  like  nitric  ether,  con- 
tain the  elements  of  an  acid. 

Ether  is  a  colorless  limpid  fluid,  having  the  specific  gravity 
of  '725.  It  boils  at  96°,  and  evaporates  rapidly  at  ordinary 
temperatures,  producing  by  its  evaporation  intense  cold.  Its 
taste  and  odor  are  pungent,  penetrating,  and  peculiar.  It  is 
very  combustible,  and  on  account  of  its  volatility  should 
never  be  brought  near  a  flame,  as  the  vapor,  when  mixed 
with  air,  is  very  explosive.  The  ether  of  the  shops  is  never 
pure,  but  contains  alcohol,  and  as  it  is  only  sparingly  soluble 
in  water,  may  be  purified  by  agitating  it  with  its  volume  of 
this  fluid,  which  combines  with  the  alcohol,  while  the  ether 
floats  on  the  surface. 

Ether  is  considerably  used  as  a  medicine  ;  internally  as  a 
powerful  stimulant ;  and  externally  as  a  refrigerant,  from  the 
cold  produced  by  its  evaporation. 

The  inhalation  of  vapor  of  ether  mingled  with  atmospheric 
air,  produces  in  the  patient  a  kind  of  intoxication,  which  is 
soon  followed  by  a  state  of  stupor,  in  which  the  subject  is 
insensible  to  external  impressions.  It  has  been  lately  em- 
ployed under  the  name  of  letheon,  and  with  wonderful  suc- 
cess, to  produce  insensibility  during  surgical  operations. 
Pure  ether  is  essential  for  this  purpose,  and  may  be  obtained 
by  washing  the  commercial  article,  as  above  described.  The 
honor  of  this  application — so  important  in  alleviating  human 
suffering, — belongs  entirely  to  this  country,  having  been  first 
suggested  by  Dr.  Charles  S.  Jackson,  of  Boston,  and  applied 
successfully  by  Mr.  Morton,  dentist,  of  the  same  city. 

The  density  of  the  vapor  of  ether  is  2581,  being  equal  to 
that  of  two  volumes  of  alcohol  vapor,  less  one  of  water. 
If  we  regard  four  volumes  of  vapor  as  representing  its 
equivalent,  its  formula  will  be  CgH^Og,  but  this  formula  is 
usually  halved,  which  gives  C4H5O. 

716.  Sulphur eted  Ether,  C4H5S,  is  a  compound  obtained 
by  the  reaction  of  hydrochloric  ether  with  sulphuret  of  po- 
tassium, C4H5C14-KS=C4H5S  +  KC1.     It  is  a  colorless  vola- 
tile liquid,  with  an  odor  resembling  that  of  garlic.     Selenium 
and  tellurium  in  like  manner  replace  the  oxygen  of  ether, 
(C4H5O,)  giving  us  analogous  seleniureted  and   sulphureted 
ethers,  (C4H5Se  and  C5H5Te.) 

717.  Olefant  Gas,  C4H4.— This  product  is  formed  when 
alcohol  is  mixed  with  so  much  sulphuric  acid,  that  the  mix- 

32 


3/4  ORGANIC    CHEMISTRY. 

lure  does  not  boil  below  320°.  The  sulphovinic  acid  then  no 
longer  takes  up  an  equivalent  of  water  in  its  decomposition ; 
but  is  directly  resolved  into  sulphuric  acid  and  olefiant  s;as, 
C4H6S2O8  =  S2H2O8+C4H4.  This  is  essentially  the  process 
already  described  for  obtaining  this  gas,  (454,)  but  a 
more  elegant  way  of  preparing  it, 
is  by  an  arrangement  similar  to 
that  used  for  producing  ether.  Sul- 
phuric acid  is  diluted  with  nearly 
one  half  its  weight  of  water,  so 
that  its  boiling-point  is  between  320° 
and  330°,  and  being  heated  in  the 
flask  a  to  ebullition,  the  vapor  of 
boiling  alcohol  is  introduced  from 
the  flask  d  by  the  tube  6,  which 
dips  a  little  way  in  the  acid.  In 
this  process,  we  may  suppose  that 
sulphovinic  acid  is  formed  with  the 
escape  of  two  equivalents  of  water 
in  vapor,  and  is  immediately  decomposed  into  sulphuric  acid 
and  olefiant  gas:  an  equivalent  of  alcohol  yields  C4H4-f  2HO. 
The  gas  is  thus  obtained  quite  pure,  and  the  process  may  be 
continued  for  any  length  of  time. 

718.  When  olefiant  gas  is  mingled  with  its  own  volume 
of  chlorine,  combination  ensues,  and  a  heavy  oily  liquid  is 
obtained  of  a  sweet  and  pungent  taste.  This  compound  was 
discovered  by  an  association  of  Dutch  chemists,  and  is  hence 
often  called  the  oil  of  the  Dutch  chemists  ;  its  formula  is 
C4H4C12.  The  action  of  chlorine  gas,  aided  by  the  sun's 
rays,  will  successively  replace  the  hydrogen  of  this  compound. 
The  different  products  are  C4H5CI,  C4H4C12,  C4H3C13,  C4H2C14, 
C4HC15  and  C4C16.  A  similar  series  is  formed,  and  in  a  simi- 
lar manner,  from  the  hydrochloric  ether,  C4H5C1.  These  two 
series  of  bodies,  although  represented  by  the  same  formulas, 
are  quite  different  in  properties,  and  are  interesting  examples 
of  isomerism.  The  final  product  of  the  action  of  chlorine 
upon  both  series  of  compounds  is  the  chlorid  of  carbon, 
C4Hg.  This  is  a  white  crystalline  solid  of  an  aromatic  odor, 
like  camphor ;  it  melts  at  320°,  and  at  a  temperature  a  little 
above  this,  may  be  distilled  unaltered.  It  is  scarcely  com- 
bustible, and  is  unchanged  by  acids  or  alkalies.  When  its 
vapor  is  passed  through  a  porcelain  tube  heated  to  redness, 
it  is  resolved  into  chlorine  gas  and  a  new  compound, 


ALCOHOL.  375 

C4C14,  which  is  a  volatile  liquid,  of  the  specific  gravity  of  1'55. 
If  the  vapor  of  this  compound  is  passed  repeatedly  through 
a  tube  at  a  bright  red  heat,  it  is  decomposed  into  chlorine  and 
C4C12.  This  body  forms  soft,  silky  crystals,  which  are  vola- 
tile and  combustible. 

Products  of  the  Oxydation  of  Alcohol. 

719.  The   first   effect   of  oxydizing  agents   upon   alco- 
hol, is  to  abstract  two  equivalents  of  its  hydrogen,  producing 
a  body  to  which  the  name  of  aldehyde  has   been   given.* 
This  is   produced  by  the  action  of  nitric  acid  and  various 
other  substances,  but  is  best  obtained   by  the  following  pro- 
cess.    Equal  weights  of  powdered  bichromate  of  potash  and 
strong  alcohol  are  introduced  into  a  retort,  and  one  and  a  half 
parts   of  sulphuric   acid    are   gradually  added   through  the 
tubulure ;  a  gentle  heat  is  then  applied,  when  a  mixture  of 
aldehyde  and  water  distils  over  and   may  be  condensed  in  a 
cold  receiver.     The  impure  product  is  mixed  with  ether,  and 
saturated  with  ammonia,  when  a  compound  of  aldehyde  and 
ammonia  separates   in  fine  crystals.     This,  decomposed  by 
dilute  sulphuric  acid,  affords  pure  aldehyde.     It  is  a  colorless 
liquid,  with  a  suffocating  ethereal  odor ;  has  a  specific  gravity 
of  -790,  and  boils  at  70°  F.     Its  formula  is  C4H402  =  alco- 
hol C4H6O2 — ELj ;  a  solution  of  potash  decomposes  aldehyde, 
and    forms  a   brown   resinous    substance,   which  is   named 
aldehyde  resin  :  this  reaction  enables  us  to  detect  the  presence 
of  aldehyde  in  liquids. 

When  a  solution  of  aldehyde,  mixed  with  a  little  ammo- 
nia, is  added  to  a  dilute  solution  of  nitrate  of  silver,  and  the 
mixture  is  heated  :  the  silver  is  reduced,  and  lines  the  vessel 
with  a  brilliant  metallic  film  which  forms  a  perfect  mirror. 
This  fact  has  been  successfully  applied  in  the  manufacture  of 
mirrors. 

720.  Aldehyde  cannot  be  preserved  unchanged,  even  in 
sealed  tubes,  but  is  slowly  changed  into  two  polymeric  com- 
pounds.    One   of  these,  elaldehyde,   is  a  dense  oily  fluid, 
which  has  none  of  the  properties  of  aldehyde.     The  den- 
sity of  its  vapor  is  three  times  that  of  aldehyde ;  and  its 
formula  is  3C4H4O2= C^H^Og.    The  other  body,  metaldehyde, 
forms  hard  white  prisms ;  it  is  formed   by  the  union  of  four 

*  From  alcohol  de  hydrogenatus. 


376  ORGANIC    CHEMISTRY. 

equivalents  of  aldehyde,  and  has  the  composition  C16H,6O8. 
When  aldehyde  is  exposed  to  the  air,  it  gradually  absorbs 
oxygen,  and  is  converted  into  acetic  acid. 

Acetic  Acid,  C4H4O4. — This  is  the  acid  of  vinegar ;  and  it 
is  produced  by  the  oxydation  of  alcohol,  or  aldehyde.  The 
latter  body  combines  directly  with  two  equivalents  of  oxygen, 
C4H4O2  +  O2=C4H4O4.  When  alcohol  is  heated  with  a  mix- 
ture of  hydrate  of  potash  and  lime,  hydrogen  gas  is  evolved 
and  acetate  of  potash  is  formed.  The  reaction  is  thus  ex- 
plained :  C4HA  +  KOHO==C4H3KO4  +  4H. 

721.  Pure  alcohol  undergoes   no  change  when  exposed  to 
the  air  alone ;  but  if  its  vapor  mixed  with  air  is  brought  into 
contact  with  platinum-black,  it  slowly  unites  with  oxygen  to 
form  aldehyde,  which  readily  absorbs  another  portion  of  oxy- 
gen, and  produces  acetic  acid.     The  oxydating  power  of  finely 
divided  platinum  has  been  before  alluded  to  :  it  absorbs  or 
condenses  great  quantities  of  gases  and  vapors  in  its  pores, 
where  they  appear  to  be  brought  together  in  such  a  state  that 
they  readily  react  upon  each  other. 

722.  The   formation  of  acetic  acid  may  be   beautifully 
shown  by  placing  a  little  platinum-black  in  a  watch-glass,  by 
the    side  of  a  small  vessel  of  alcohol,  covering  the  whole 
with  a  bell-glass,  and  setting  it  in  the   sun-light.     In  a  short 
time  the  vapor  of  acetic  acid  will  condense  on  the  sides  of 
the  glass,  and  run   down  in  drops ;  and  if  we  occasionally 
admit  fresh  air  by  raising  the  bell-jar,  the  whole  of  the  alco- 
hol will  be  acidified  in  a  few  hours. 

The  change  consists  in  the  loss  of  two  equivalents  of  hy- 
drogen, and  the  addition  of  two  of  oxygen. 

In  the  ordinary  process  for  vinegar,  alcoholic  liquors,  as 
wine  and  cider,  are  exposed  to  the  air  in  open  vessels.  Although 
a  mixture  of  pure  alcohol  and  water  does  not  absorb  oxygen 
from  the  air,  a  small  portion  of  any  ferment,  as  vinegar 
already  formed,  or  the  substance  called 
mother  of  vinegar,  enables  it  to  combine  with 
oxygen.  In  this  process,  the  essential  thing 
is  a  free  supply  of  air,  and  a  proper  temper- 
ature. In  the  manufacture  of  vinegar  on  the 
I  large  scale,  this  is  secured  by  causing  the 
liquor  (b)  to  trickle  from  threads  of  cotton 
drawn  through  holes,  over  shavings  of  beech- 
wood  previously  soaked  in  vinegar,  and  con- 
tained in  a  large  cask  with  holes  in  its  sides,  (c  c  c  c,)  so  as 


ALCOHOL.  377 

to  admit  a  free  circulation  of  air.  Jn  this  way  a  vast  surface 
is  exposed,  and  the  absorption  of  oxygen  is  very  rapid, 
causing  an  elevation  of  20°  or  30°  in  the  temperature.  The 
liquid  is  passed  through  this  apparatus  four  or  five  times  in 
the  course  of  twenty-four  hours,  in  which  time  the  change 
of  the  alcohol  into  vinegar  is  generally  complete.  The  pro- 
duct is  collected  in  the  vessel  a. 

723.  Acetic   acid    is  also  obtained  by  distilling  wood  in 
close  vessels ;  the  volatile  ingredients  are  expelled  and  char- 
coal alone  remains ;  the  products  are,  besides  carbonic  acid 
and  carbureted    hydrogen,  a    large  quantity  of  acetic  acid, 
mixed  with  oily  and  tarry  matters,  from  which  it  is  separated 
mechanically.     The  acid  thus  prepared  is  known  as  pyrolig- 
neous  acid,  and  is  largely  used   in  the  arts  of  dyeing  and 
calico-printing,    but   being   contaminated    by   empyreumatic 
oils,  is  not  fit  for  the  purposes  of  domestic  economy.     By 
combining  it  with  bases,  salts  are  obtained,  which,  when  de- 
composed, afford  a  pure  acid. 

724.  By  distilling  dried  acetate  of  soda  with  strong  sul- 
phuric acid,  a  very  concentrated   acid    is   obtained,  which, 
when  exposed  to  cold,  deposits  crystals  of  pure  acetic  acid, 
C4H4O4.     The  pure  acid  is  solid  below  60°  F. ;  when  liquid 
it  has  a  specific  gravity  of  1-063,  and  boils  at  248°.     It  is 
perfectly  soluble  in  water,  alcohol,  and  ether ;  it  has  a  pun- 
gent fragrant  odor   and   a  very  acid  taste,  and  when  applied 
to  the  skin  is  highly  corrosive.     The  acid  is  monobasic ;  all 
its  salts  are  soluble  in  water. 

Acetates. 

725.  Acetate  of  Potash  (C4H3KO4),  is  easily  prepared  by 
neutralizing  acetic  acid  with  carbonate  of  potash.     It  is   a 
very  soluble  deliquescent  salt,  and  is  employed  in  medicine. 
Acetate  of  soda  (C4H3NaO4),  forms  large  crystals  with  six 
equivalents  of  water.     It  is  prepared  in  large  quantities  from 
pyroligneous  acid.     The  salt  is   healed  to  destroy  the  oily 
matter,  and  then  affords  by  its  decomposition  a  pure  acid. 
Acetate  of  ammonia  (C4H4O4+NH3),  is  used  in  medicine  by 
the   name  of  the  spirit  of  Mindereus.     It  is   prepared  by 
saturating   acetic   acid  with    ammonia,  and    is   exceedingly 
soluble  and  volatile.     The  acetate  of  zinc  is  a  beautiful  white 
salt,  and  is  employed  as  a  tonic  and  astringent.    The  acetate 
of  alumina  is  much  used  in  dyeing ;  it  is  obtained  by  dccom- 

32* 


378  ORGANIC    CHEMISTRY. 

posing  a  solution  of  alum  by  one  of  acetate  of  lead  ;  sulphate 
of  lead  precipitates,  and  acetate  of  alumina  with  acetate  of 
potash  remains  in  solution.  The  acetate  and  sesqui-acetate 
of  iron  are  prepared  in  a  similar  manner,  and  are  largely 
employed  in  calico-printing  and  dyeing.  The  constitution  of 
the  sesqui-acetates  has  been  already  explained  (676). 

726.  Acetate  of  Lead,   C4H3Pb,O4.  —  This  salt  is  well 
known  under  the  name  of  sugar  of  lead.     It  is  prepared  by 
dissolving  oxyd  of  lead  (litharge)  in  acetic  acid,  and  crystal- 
lizes with  three  equivalents  of  water,  which  are  expelled  by 
gentle  heat.     It  is  a  white  salt,  with  a  very  sweet  and  astrin- 
gent taste,  and  is  often  employed  as  a  medicine ;  but  is  poi- 
sonous, and  should  be  used  internally  with  caution. 

The  acetate  of  lead  has  a  great  tendency  to  combine  with 
oxyd  of  lead,  with  which  it  forms  several  definite  compounds. 
These  are  generally  designated  as  basic  salts,  but  should  be 
carefully  distinguished  from  the  salts  containing  more  than 
one  equivalent  of  base,  which  are  formed  by  bibasic  and 
tribasic  acids.  In  these  last,  the  metal  replaces  the  hydrogen 
of  the  acid,  but  in  the  basic  acetates,  the  neutral  salt  combines 
directly  with  the  oxyd.  To  distinguish  them,  the  term  sur- 
basic  is  applied,  and  the  compound  of  the  acetate  with  two 
equivalents  of  oxyd  of  lead  is  called  the  bi-surbasic  acetate 
of  lead.  Three  of  these  compounds  are  known,  in  which 
the  acetate  is  combined  with  one-half,  two,  and  five  equivalents 
of  oxyd.  The  second  is  the  only  one  of  importance. 

727.  Bi-surbasic  Acetate  of  Lead,  C4H3PbO4-f  2PbO.— 
This  salt,  commonly  called  the  tribasic  acetate,  is  obtained 
by  digesting  a  solution  of  six  parts  of  the  acetate  with  seven 
of  litharge :  the  oxyd  is  dissolved,  and  the  liquid  affords,  by 
evaporation,  a  salt  crystallizing  in  long  needles.     It  is  also 
slowly  formed  when  metallic  lead  is  digested  in  an  open  vessel 
with  a  solution  of  the  acetate,  oxygen  being  absorbed  from 
the  air.     The  salt  is  very  soluble  in  water,  and  its  solution 
has  an  alkaline  reaction  :  it  is  well  known  in  pharmacy  as 
Goulard's  Extract,  or  solution  of  lead.     When  exposed  to 
the  air,  it  absorbs  carbonic  acid,  and  the  two  equivalents  of 
oxyd  of  lead  are  precipitated  as  a  carbonate.     This  reaction 
enables  us  to  explain  the  formation  of  white  lead,  (606.) 

758.  A  process  frequently  employed  is  to  mix  litharge  and 
about  T^-oth  of  sugar  of  lead  into  a  thin  paste  with  water ; 
the  mixture  is  gently  heated,  and  a  current  of  carbonic  acid 
is  passed  through  it.  The  acetate  of  lead  dissolves  a  portion 


ALCOHOL.  379 

of  the  oxyd  to  form  the  tribasic  salt;  this  is  immediately 
decomposed  by  the  carbonic  acid,  which  precipitates  carbonate 
of  lead,  and  leaves  the  acetate  free  to  dissolve  a  new  portion 
of  oxyd.  In  this  way  the  smallest  quantity  of  the  acetate  is 
able  to  convert  a  large  portion  of  the  oxyd  into  carbonate, 
and  at  the  end  of  the  process  to  remain  unaltered. 

729.  In  the  ordinary  process,  the  plates  of  lead  are  ex- 
posed to  the  action  of  acetic  acid,  moisture,  air,  and  carbonic 
acid  from  the  fermenting  tan.     The  lead   immediately  be- 
comes covered  with  a  film  of  oxyd  by  the  action  of  the  air. 
This  is  dissolved  by  the  vapor  of  acetic  acid,  and  forms  a 
solution  of  neutral  acetate,  which  moistens   the  plates   and 
gradually  acts  upon  them,  forming  by  the  aid  of  the  atmo- 
spheric oxygen,  the  basic  acetate.     This  is  decomposed  by 
the  carbonic  acid,  in  the  same  manner  as  in  the  last  process, 
and  the  neutral  acetate  is  again  set  free  to  act  upon  the  me- 
tallic lead  ;  the  process  goes  on  until  all  the  lead  is  carbonated. 
In  this  way  a  small  quantity  of  acetic  acid  will,  under  favor- 
able circumstances,  convert  a  hundred  times  its  weight  of 
lead  into  carbonate  in  a  few  weeks. 

730.  Acetate  of  Copper,  C4H3C4(X. — This   salt  is  quite 
soluble,  and  forms  beautiful  green  crystals  of  the  monoclinate 
system,  containing  one  equivalent  of  water.     The  acetate  of 
copper  forms  several  surbasic  salts  which  are  insoluble  in  water. 
The  fine  green  pigment  called  verdigris  is  a  mixture  of  two 
or  more  of  these ;  all  of  these  copper  salts  are  very  poisonous. 

The  Acetate  of  Silver  (C4H3AgO4),  crystallizes  in  white 
scales,  and  is  the  least  soluble  of  the  acetates. 

731.  Chloracetic  Acid,  C4C13HO4. — When  acetic  acid  is 
placed  in  a  vessel  of  chlorine  gas,  and  exposed  to  the  sun- 
light, three  equivalents  of  its  hydrogen  are  removed  in  the 
form  of  hydrochloric  acid,  and  three  of  chlorine  substituted 
in  their  place.     The  chloracetic  acid  closely  resembles  tne 
acetic,  and  its  salts  correspond  to  the  acetates  of  the  same 
bases.     A  solution  of  any  chloracetate  is  decomposed  by  an 
amalgam  of  potassium :    the  chlorine  is  removed,  and  we 
obtain  chlorid  of  potassium  and  ordinary  acetate  of  potash. 

732.  Acetic   Ether,   C8H8O4.  —  This    is    formed    by    the 
direct  action  of  acetic  acid  on  alcohol ;  but  is  best  obtained 
by  distilling  five  parts  of  acetate  of  soda,  eight  of  sulphuric 
acid,  and   three  of  alcohol.     It  is  a  very  fragrant  volatile 
liquid ;  the  odor  of  vinegar  formed  from  fermented  liquor  is 
due  to  a  little  acetic  ether.     It  contains  the  elements  of  one 


380  ORGANIC    CHEMISTRY. 

equivalent  of  alcohol,  and  one  of  acetic  acid,  less  two  of 
water,  C4H6O2  +  C4H4O4=C8H8O4-f  2HO. 

733.  When  acetic  acid  or  acetates  are  decomposed  by 
heat,  a  volatile  liquid  called  acetone  is  obtained  :  it  is  derived 
from  the  elements  of  two  equivalents  of  acetic  acid,  by  the 
abstraction  of  two  of  carbonic  acid   gas  and  two  of  water, 
2(C4H4O4)-(2CO2+2HO)=C6H6O2.     The  vapor  of  acetic 
acid,  when   passed   through  an  ignited   tube,   is  completely 
resolved  into  these  substances.     Acetone  is  a  very  volatile 
liquid,  of  specific  gravity  -793,  and  has  a  pungent  and  peculiar 
odor.     It   is   readily  soluble   in   water,  alcohol   and   ether. 
When  distilled   with  a  mixture  of  chromate  of  potash  and 
sulphuric  acid,  it  yields  acetic  acid. 

By  the  action  of  an  excess  of  potash  upon  an  acetate,  it  is 
decomposed  into  carbonic  acid  and  marsh  gas,  C4H4O4== 
2CO2+C2H4,  (451.) 

WOOD-SPIRIT,  C2H402. 

734.  This  substance  is  a  product  of  the  destructive  dis- 
tillation of  wood :  when  the  crude  pyroligneous  acid  (723) 
is   saturated    by    lime   and   distilled,   impure  wood-spirit   is 
obtained,  and   may   be  afterwards   purified   by  repeated  dis- 
tillations.    It  is  a  colorless  liquid,  of  a  peculiar  and  some- 
what unpleasant  odor,  and  a  hot  pungent   taste.     It   has  a 
specific  gravity  of  -798,  and  boils  at  152°;  it  is  very  com- 
bustible, and  burns  with  a  pale  blue  flame.     Like  alcohol,  it 
mixes  in  all  proportions  with  water.     It  is  occasionally  used 
in  the  arts  for  dissolving  resins,  and  making  varnishes ;  and 
the  pure  wood-spirit  has  lately  acquired   some  celebrity  in 
the  treatment  of  phthisis,  under  the  name  of  wood-naphtha. 

This  substance  is  known  in  commerce  as  pyroxylic 
spirit;*  from  its  resemblance  to  alcohol,  it  has  been  called 
methylic  alcohol,*  and  the  name  of  methal  is  also  employed. 

Wood-spirit  is  closely  affined  to  alcohol  in  all  its  chemical 
relations.  By  the  action  of  acids  it  gives  rise  to  ethers, 
which  in  their  properties  and  mode  of  formation  are  so 
similar  to  the  corresponding  bodies  from  alcohol,  that  what 
has  been  said  of  these  will  apply  to  them  in  every  respect. 
With  bibasic  acids  it  forms  methylic  acids  similar  to  the 
vinic. 

*  Pyroxylic  spirit,  from  pur,  fire,  and  hulon,  wood,  in  allusion  to 
its  origin ;  and  methylic  alcohol,  from  metku,  wine,  and  hulon  :  the 
wine  or  alcohol  of  wood. 


WOOD-SPIRIT.  381 

735.  The  Nitric  Methylic  Ether,  C2H3NO6,  is  formed  by 
distilling  wood-spirit  with  nitre  and  sulphuric  acid.     It   is  a 
heavy  oily  fluid,  which  by  the  action  of  a  solution  of  potash 
takes  up  the  elements  of  two  equivalents  of  water,  and  yields 
nitrate  of  potash  and  wood-spirit.     Its  vapor,  when  heated  to 
250°,  explodes  with  great  violence. 

Hydrochloric  Methylic  Ether,  C2H3C1,  is  obtained  in  the 
form  of  a  gas,  having  a  sweet  ethereal  taste,  and  a  specific 
gravity  of  1*731.  The  compounds  containing  bromine  and 
iodine  are  liquids. 

736.  Sulphuric  Methylic  Ether.—- This  compound,  the 
analogue  of  which   is   unknown    in   the  alcohol   series,   is 
obtained   by  distilling  wood-spirit  with  eight  or  ten  parts  of 
sulphuric  acid.     It  is  a  tasteless,  oily  fluid,  which  has  an  allia- 
ceous odor ;  boils  at  370°,  and  has  a  specific  gravity  of  1-324. 
It  is  formed  from  an  equivalent  of  sulphuric  acid  and  two 
of  wood-spirit,  by  the  loss  of  four  of  water,  S2H2O8-f-2C2H4 
O2==C4H6S2O8  +  4HO.    By  the  action  of  boiling  water  it  takes 
the  elements  of  two  equivalents  of  that  liquid,  and  is  in  part 
decomposed,  yielding   wood-spirit  and   sulphomethylic  acid, 
and  by  excess  of  caustic  potash  the  decomposition  is  com- 
plete.    By  the  action  of  ammonia  a  white  crystalline  com- 
pound is   formed,   which    is   called  sulphamethylane ;    one 
equivalent  of  the   ether   and   one  of  ammonia,    yield   one 
equivalent  of  the   new  substance  and   one  of  wood-spirit, 
C4H6S2O8  +  NH3=C2H5NS2O6  +  C2H4O2.      Its  nature  will  be 
understood   by  referring  to  what  we  have  said  of  the  simi- 
larity   between   the  ethers   and  amides,  (705.)      We   have 
represented  the  former  as  derived  from  alcohol  and  an  acid, 
by  the  loss  of  two  equivalents  of  water ;  and  the  amides,  in 
the  same  manner,  are  formed   from  ammonia  and  an  acid. 
Sulphamethylane  is  an  ether- amide,  and  is  formed  from  one 
equivalent  of  ammonia  and  one  of  wood-spirit,  with  one  of 
a  bibasic  acid,  by  the  separation  of  four  of  water ;  it  therefore 
corresponds  to  the  neutral  sulphuric  methylic  ether,  and  like 
it  is  decomposed  by  potash,  taking  up  the  elements  of  four 
equivalents  of  water,  and  yielding  sulphuric  acid,  wood-spirit, 
and  ammonia. 

737.  Sulphomethylic  Acid,  C2H:S2O8. — This  acid  is  ob- 
tained by  a  similar  process   to  that   for  the  sulphovinic,  and 
like  it  is  a  monobasic  acid,  forming  soluble  salts  with  lime  and 
baryta.     It  is,  however,  more  permanent  than  the  sulpho- 
vinic acid,  and  may  be  obtained  in  small  crystals  which  arc 
very  soluble  in  water. 


382  ORGANIC    CHEMISTRY. 

738.  When  sulphomethylic  acid   is  decomposed  by  heat, 
it  undergoes  a  change  similar  to  the  sulphovinic  acid,  and 
evolves  a  colorless  gas,  which  is  wood-spirit,  minus  the  ele- 
ments of  one  equivalent  of  water,  C2H402— HO  =  C2H3O. — 
This  corresponds  precisely  to  the  ether  of  alcohol,  and  is  called 
wood  ether,  methylic  ether  or  mether :  it  is  not  condensed 
by  intense  cold  ;  has  a  pungent  taste  and  odor,  and  is  soluble 
in  water  and  alcohol. 

739.  In  the  same  manner  as  hydrochloric  ether  may  be 
considered  as  derived  from  acetene,  which  is  alcohol  minus 
two  equivalents  of  oxygen,  the  corresponding  compounds  of 
wood-spirit  may  be  derived  from  marsh  gas,  which  is  C2H4O2 — 
O2=C2H4.     The  name  of  formene  is  hence  given  to  this  gas. 
Several  compounds  formed  from  the  action  of  chlorine  and 
its   congeners  upon  bodies   of  the  alcohol  and  wood-spirit 
series,  may  be  viewed  as  formene,  in  which  a  part  of  the 
hydrogen  is  replaced  by  chlorine,  bromine,  or  iodine. 

Chloroform  ;  Tri-chlorinized  Formene,  C2HC13. — This  is 
formed  when  alcohol  or  wood-spirit  is  distilled  with  a  solu- 
tion of  two  or  three  parts  of  chlorid  of  lime,  in  twenty  parts 
of  water.  It  is  a  heavy  oily  liquid,  nearly  insoluble  in 
water,  which  boils  at  141°,  and  has  a  specific  gravity  of  1'48. 
It  has  a  very  sweet  and  pungent  taste,  and  its  alcoholic  solu- 
tion is  employed  in  medicine  under  the  name  of  chloric 
ether.  Bromine  forms  a  similar  compound. 

lodiform  ;  Tri-iodized  Formene,  C2HI3,  is  obtained  when 
iodine  acts  upon  an  alcoholic  solution  of  potash.  It  crystal- 
lizes in  bright  yellow  scales,  and  has  a  pungent  aromatic 
taste.  All  of  these  compounds  are  decomposed  by  an  alco- 
holic solution  of  hydrate  of  potash,  affording  a  compound  of 
the  salt-radical  with  potassium,  and  formate  of  potash, 
C2HC13+ 4KO==  3KC1+ C2HK04. 

When  chloroform  is  exposed  to  the  action  of  chlorine  gas, 
aided  by  the  sun's  light,  the  remaining  equivalent  of  hydro- 
gen is  removed  and  a  chlorid  of  carbon  is  obtained,  C2C41,  or 
perchlorinized  formene. 

Oxydation  of  Wood- Spirit. 

740.  When  the  vapor  of  wood-spirit  mixed  with  air   is 
exposed  to  the  action  of  platinum-black,  it  loses  hydrogen 
and  absorbs  oxygen,  producing  water  and  formic  acid.     This 
is  derived  from  wood-spirit  by  a  reaction  exactly  similar  to 
that  producing  acetic  acid  from  alcohol ;  two  equivalents  of 


WOOD-SPIRIT.  383 

hydrogen  combine  with  oxygen  to  form  water,  and  two  of 
oxygen  unite  with  the  residue,  (C2H4O2— H2)  +  O2=C2H2O4. 
The  intermediate  product  of  this  reaction,  corresponding  to 
aldehyde,  has  not  been  obtained.  When  wood-spirit  is  heated 
with  a  mixture  of  hydrate  of  potash  and  lime,  hydrogen  gas 
is  evolved,  and  formate  of  potash  is  produced. 

741.  Formic  acid  occurs  as  a  secretion  of  the  red-ant, 
(Formica  rufa,)  from  whence  it  derives  its  name,  and  may 
be  obtained  by  distilling  the  ants  with  water.     It  is  also  a 
product  of  the  oxydation  of  sugar,  and  many  other  organic 
substances,  and  is  best  prepared  by  the  following  process. 
800  grains  of  bichromate  of  potash  and   300  of  sugar,  are 
dissolved  in  seven  ounces  of  water.     The  mixture  is  placed 
in  a  retort,  and  one   measured   ounce  of  sulphuric  acid  very 
gradually  added ;  it  is  then  distilled  with  a  gentle  heat,  until 
three  ounces  of  liquid   are  obtained.     This   is  dilute  formic 
acid,  and  may  be  used  to   form  salts,  which  when  decom- 
posed afford  a  strong  acid. 

The  pure  acid  is  obtained  by  passing  sulphureted  hydrogen 
gas  over  dry  formate  of  lead  ;  sulphuret  of  lead  and  formic 
acid  are  produced.  The  action  is  aided  by  a  gentle  heat, 
and  the  acid  distils  over.  It  is  a  colorless  liquid,  of 
specific  gravity  1-235,  which  boils  at  212°,  and  at  32°  crys- 
tallizes, like  acetic  acid,  in  shining  plates.  It  fumes  in  the 
air,  and  has  a  very  pungent  odor,  resembling  that  of  ants  ;  it 
is  powerfully  acid  and  very  corrosive,  instantly  blistering  the 
skin.  When  this  acid  or  its  salts  are  heated  with  strong 
sulphuric  acid,  it  is  decomposed  with  the  evolution  of  pure 
carbonic  oxyd  gas,  C2H2O4=2CO  +  2HO.  When  formic 
acid  or  a  formate  is  heated  with  solutions  of  the  noble  metals, 
it  reduces  them,  and  is  itself  decomposed  with  the  evolution 
of  carbonic  acid  gas. 

The  formates  closely  resemble  the  acetates.  The  formate 
of  potash ,  C2HKO4,  is  very  soluble.  The  formate  of  silver, 
C2HAgO4,  crystallizes  in  scales  ;  when  its  solution  is  boiled, 
the  silver  is  precipitated  in  the  metallic  state,  while  carbonic 
acid  and  carbonic  oxyd  gases  escape,  C2HAgO4— Ag-f  HO-f 
CO2+CO. 

AMYLIC    ALCOHOL,  Ci0H12O2. 

742.  In  the  distillation  of  spirit  made  from  potatoes,  the 
last  portions  of  the  liquid  are  rendered  milky  by  a  peculiar 
oily  substance  which  separates  on  standing,  and  to  which  the 


384  ORGANIC    CHEMISTRY. 

name  of  potato  oil,  or  fusel  oiZ,  is  given.  It  does  not  exist  in 
the  vegetable,  but  is  a  product  of  the  fermentation,  and  is 
also  found  in  the  spirit  obtained  from  the  fermentation  of 
raisins  and  the  juice  of  beets.  It  is  freed  from  alcohol  by 
agitation  with  water,  and  is  afterwards  purified  by  distillation. 
When  pure  it  is  a  colorless  liquid,  which  is  insoluble  in  water, 
has  u  specific  gravity  of  -818,  and  boils  at  269°.  It  has  a 
burning  taste,  and  a  pungent  disagreeable  odor,  which  excites 
coughing,  and  often  distressing  nausea. 

It  closely  resembles  alcohol  and  wood-spirit  in  its  chemical 
relations,  ahd  has  hence  received  the  name  of  amylic  alcohol* 
or  amylol.  By  the  action  of  acids  it  yields  ethers,  which  are 
similar  to  those  derived  from  alcohol. 

743.  The  Acetic  Amylic  Ether  (C14HI4O4),  is  obtained  by 
distilling  potato  oil  with  a  mixture  of  acetate  of  potash  and 
sulphuric  acid.     One  equivalent  of  amylic  alcohol,  and  one 
of  acetic  acid,  yield   one  of  the  ether,  and   two  of  water ; 
C10H12O2  +  C4H4O4=C14H14O4  +  :2HO.      It  is  a  colorless  fra- 
grant liquid,  which  is  decomposed  by  an  alcoholic  solution  of 
potash,  forming  acetate  of  potash  and  potato  oil. 

Hydrochloric  Amylic  Ether  (C10H,,C1),  is  formed  when 
potato  oil  is  distilled  with  hydrochloric  acid.  It  may  be 
viewed  as  a  substitution  product  of  valerene  (CIOHI2),  a  body 
corresponding  to  acetene.  By  the  action  of  nitric  acid  upon 
potato  oil,  a  liquid  is  obtained  corresponding  to  the  hypo- 
nitrous  ether  from  alcohol,  which  may  be  considered  as  nitric 
valerene. 

744.  With  sulphuric  acid,  amylic  alcohol  forms  a  coupled 
acid  which  is  quite  similar  to  the  sulphovinic,  and  is  called 
sulphamylic  acid.     It  is  derived  from  one  equivalent  of  sul- 
phuric acid  and  one  of  the  amylic  alcohol,  by  the  abstraction 
of  the  elements  of  water ;  and  by  the  action  of  alkalies  is 
decomposed  with  the  regeneration  of  the  potato  oil   and  the 
formation  of  a  sulphate. 

745.  The  Amylic  Ether  or  Amylether  (C,0H,,O),  has  been 
obtained,  but  its  characters  have  not  been  studied.     It  appears 
to  be  formed  by  the  distillation  of  sulphamylic  acid. 

When  potato  oil  is  distilled  with  an  excess  of  sulphuric 
acid,  a  volatile  oily  liquid  is  obtained,  which  is  formed  from 
the  amylic  alcohol  by  the  abstraction  of  the  elements  of  two 

*  From  amyhcm,  starch,  as  it  was  supposed  to  be  derived  from 
the  fermentation  of  the  starch  of  the  potatoes. 


AMYLIC    ALCOHOL.  385 

equivalents  of  water.  It  is  called  paramilene,  and  has  the 
formula  C10H10=C10H,2O2  —  2HO:  it  corresponds  precisely  to 
olefiant  gas  in  the  alcohol  series. 

Oxydation  of  Amylic  Alcohol  or  Potato  Oil. 

746.  When  this  substance  is  exposed  to  the  air,  it  slowly 
absorbs  oxygen,  and  becomes  acid  :  the  change  is  effected 
much  more  rapidly  when  the  oil  is  dropped  upon  platinum- 
black.     The  product  of  this  oxydation  is  valerianic  acid 
(C,0H,0O4)  :  it  is  formed  by  a  process  similar  to  that  yielding 
acetic  acid.    An  equivalent  of  the  oil  loses  two  of  hydrogen, 
which  combine  with  exygen,  producing  water,  and  the  residue 
takes   two   of  oxygen    to    form   the   acid,   C,0Hi2O2-f  4O= 
C,0H10O4-f  2HO.     The  acid  is  also  formed  with  disengage- 
ment of  hydrogen  gas,  when  the  oil  is  heated  with  hydrate 
of  potash  ;  valerianate  of  potash  is  obtained,  which   is  de- 
composed by  distilling  with  dilute  sulphuric  acid.     This  acid 
is    identical  with   that  which    exists   in    the  Valeriana  offi- 
cinalis,  and  is  obtained   by  distilling  the  root  of  that  plant 
with  water.     It  is   to  this  acid   that  the  valerian  owes  its 
medicinal  properties.     Valerianic  acid  has  been  found  in  a 
free  state  in  cheese,  and  it  is  to  its  presence  that  the  flavor  of 
old  cheese  is  in  part  due. 

747.  Valerianic  acid  is  a  colorless  oily  fluid,  which  boils  at 
347°,  and  has  a  specific  gravity  of  '937.     Its  taste  is  sharp 
and  acid,  and  its  odor  powerful  and  disagreeable,  resembling 
that  of  valerian.     Water  dissolves  a  large  quantity  of  it,  and 
it  is  readily  soluble  in  alcohol.     Like  the  acetic  and  formic 
acids,  it  is  monobasic  :  its  salts  are  all  soluble  in  water,  and 
have  a  slight  odor  of  valerian.    'The  valerianate  of  potash 
is  very  soluble  and  deliquescent  ;  that  of  baryta  (CIOH9BaO4), 
crystallizes  in  fine  transparent  prisms.     The  valerianate  of 
zinc  (C,0H9ZnO4),  is  prepared  by  neutralizing  the  acid  with 
carbonate  of  zinc,  and  crystallizes  in  white  scales.    It  is  em- 
ployed in  medicine  as  a  substitute  for  valerian,  the  peculiar 
medicinal  powers  of  which  it  possesses  in  a  high  degree. 

By  the  action  of  chlorine  upon  this  acid,  a  portion  of  its 
hydrogen  is  replaced,  and  trichlorinized  valerianic  acid 
is  formed,  which  corresponds  to  the  chloracetic  acid. 


ETHAL, 

748.  This  substance   is   obtained   by   the   action   of  the 
hydrate  of  potash  upon  spermaceti  :  it  is  a  white  crystalline 
33 


386  ORGANIC    CHEMISTRY. 

solid,  which  fuses  at  118° :  is  insoluble  in  water,  but  soluble 
in  alcohol,  and  may  be  volatilized  without  decomposition. 
In  its  chemical  characters  it  is  closely  related  to  alcohol : 
by  the  action  of  perchlorid  of  phosphorus,  it  yields  a  com- 
pound which  corresponds  precisely  to  the  hydrochloric  ether 
from  alcohol :  it  has  the  composition  C^H^Cl.  Ethal,  when 
heated  with  sulphuric  acid,  combines  with  it  to  form  a 
coupled  acid,  which  is  called  the  sulphocetic  or  sulphethalic  : 
it  is  monobasic,  and  is  formed  precisely  like  the  sulphovinic 
from  one  equivalent  of  sulphuric  acid  and  one  of  ethal,  by 
the  abstraction  of  two  of  water.  When  ethal  is  distilled  with 
anhydrous  phosphoric  acid,  it  loses  the  elements  of  two 
equivalents  of  water,  and  yields  a  carbo-hydrogcn,  C^H^, 
which  is  called  cetene,  and  is  polymeric  of  olefiant  gas. 

749.  The  substance  known  as  spermaceti  or  cetene,  may 
be  regarded  as  the  aldehyde  of  ethal.    It  is  found  in  immense 
cavities  in  the  head  of  the  sperm  whale,  where  it  is  mixed 
with  a  portion   of  oil.     The   fluid    parts   arc   removed    by 
pressure,  and  the  remaining  oil  dissolved  by  washing  in  a 
dilute  solution  of  potash.     Pure  spermaceti  fuses  at  120°, 
and  forms  in  cooling  radiated  masses  of  beautiful  crystalline 
plates  with  a  pearly  lustre.     It   is    insoluble  in  water,  but 
soluble  in  strong  alcohol  and  ether.     Its  formula  is  C^H^C^, 
equal  to  ethal  minus  two  equivalents  of  hydrogen.     When 
fused  with  a  gentle  heat  and  mixed  with  hydrate  of  potash, 
it  is  decomposed,  yielding  ethal  and  the  potash  salt  of  ethalic 
acid,  SC^A  +  KO,HO = C^HaA  +  C32H31KO4. 

750.  When  ethal  is    heated   with    hydrate   of  potash   to 
about  400°,    hydrogen    gas  is   evolved,    and   ethalic   acid 
is  formed.     The  reaction  is  similar  to  that   producing  acetic 
acid  from  alcohol,  (C^UA^U^  +  O^CAO,.     This  is 
also  obtained  when  a  mixture  of  spermaceti  and   potash  is 
heated  to  the  same  temperature :  the  aldehyde  in  this  case 
simply  takes  two  equivalents  of  oxygen  to  form  the  acid. 

The  ethalic  acid  is  a  white  solid,  lighter  than  water ;  it 
fuses  at  131°,  and  forms  on  cooling  a  brilliant  radiated 
crystalline  mass  ;  it  is  soluble  in  alcohol,  but  insoluble  in 
water.  This  acid  is  monobasic :  the  ethalates  with  an 
alkaline  base  are  soluble ;  the  others  are  insoluble  in  water. 
Ethalic  acid  belongs  to  a  class  of  fatty  acids  yet  to  be 
described,  and  its  character  and  relations  will  be  again 
alluded  to. 


RELATIONS  OF  THE  PRECEDING  BODIES.        387 

On  the  Relations  of  the  preceding  Bodies. 

751.  The  four  classes  of  compounds   last  described  have 
been  shown  to  be  nearly  affined  in  their  chemical  characters  : 
they   may    be  viewed   as    members    of  a   group  of  which 
common  alcohol  or  spirits  of  wine  is  the  representative,  and 
may  be  designated  by  the  common  name  of  alcohols.     They 
unite  with  sulphuric  acid,  with  separation  of  the  elements  of 
water,  to  form  coupled  acids  —  yield  ethers  by  the  action  of 
other  acids  ;  aldehydes  by  the  abstraction  of  two  equivalents 
of  hydrogen  ;  monobasic  acids  which  have  the  composition 
of  the  aldehydes  plus  two  equivalents  of  oxygen,  and  hydro- 
carbons   which    correspond    to    the    alcohols,    minus    two 
equivalents  of  water.     Although  the  whole  of  these  charac- 
teristics are   not  developed  in  any  one  of  the  group,  they 
agree  in  a  sufficient  number  to  establish  their  close  affinities. 
These  relations,  which  depend  upon  similarity  of  constitution, 
are  designated   as  homologous,  and   the  alcohols  are  called 
homologues,  or   homologous  bodies.      This    relation    is    to 
be  carefully   distinguished    from   analogy,   which   refers  to 
external  or  accidental  resemblance.     To  illustrate  this  by  an 
example  —  alcohol   resembles   acetone  in  being  volatile,  very 
combustible,  and  soluble  in  water,  and  ethal   is  like  sperma- 
ceti  in   being   solid,   crystalline,   and    insoluble  ;    but  these 
external  resemblances  are  only  analogies,  and  if  we  examine 
the  constitution  of  the  bodies,  we  shall  find  that  the  volatile, 
soluble   alcohol,    and   the   solid,  crystalline   ethal,  are   the 
bodies  which  are  really  affined  to  each  other. 

752.  In  the  alcohols  the  oxygen  is  always  equal  to  two 
equivalents,  and  the  proportion  of  hydrogen  is  greater  than 
that  of  the  carbon  by  two;   so  that  in  effect  their  decom- 
position affords  two  equivalents  of  water,  and  a  compound 
of  equal  equivalents  of  carbon  and   hydrogen.     The  acids 
derived   from   them  all  contain  four  of  oxygen,  and  equal 
equivalents  of  the  other  elements. 


Wood-spirit,  C2H4O2  Formic  acid, 

Alcohol,         C4H602  Acetic     "  C4H4O4 

Potato  oil,      CioHiaOa  Valerianic  acid, 

Ethal,  C32H34O2  Ethalic         " 


From  these  and  many  other  instances  we  arrive  at  the 
important  law  that  in  a  class  of  homologous  bodies  the  pro- 
portion of  oxygen  is  invariably  the  same  ;  and  that  the  equi- 
valents of  carbon  and  hydrogen  bear  a  similar  proportion  to 


388  ORGANIC    CHEMISTRY. 

each  other,  being  either  equal,  or  varying  by  a  common 
difference.  The  amount  of  nitrogen,  when  this  element  is 
present  in  homologues,  is  like  the  oxygen  invariable:  and 
when  chlorine  replaces  hydrogen,  it  is  subject  to  the  same  law 
as  hydrogen  itself;  the  like  is  true  of  sulphur  replacing 
oxygen. 

BITTER  ALMOND  OIL,  C14H602. 

753.  Benzoilol,  Essential  Oil  of  Bitter  Almonds. — This 
oil  does  not  exist  ready  formed  in  the  almonds,  but  is  pro- 
duced by  the  reaction  of  certain  principles  contained  in  the 
kernel  when  aided  by  the  presence  of  water.     It  is  obtained 
by  bruising  bitter  almonds  into  a  paste  with  water,  and  dis- 
tilling the  mixture,  when   the  oil   passes  over,  with   hydro- 
cyanic acid  and  other  impurities.    It  is  purified  by  redistilling 
it  from  a  mixture  of  protochlorid  of  iron  and  lime.     It  is  a 
colorless  oily  liquid,  of  a  pungent  burning  taste,  and  very 
fragrant  odor,  like  that  of  bruised  bitter  almonds.    It  boils  at 
356°,  but  its  vapor  distils  over  with  that  of  water  at  212°; 
its  specific  gravity  is  1*073.     It  is  often  used   in   flavoring 
articles  of  food,  but  the  crude  oil  which  is  sold  for  this  pur- 
pose   is   exceedingly   poisonous :    from   the   experiments  of 
Pereira  it  appears  that  the  pure  oil  is  harmless. 

Sulphureted  Benzoilol. —  By  the  action  of  hydro-sul- 
phuret  of  ammonia  upon  bitter  almond  oil,  its  oxygen  is  re- 
placed by  sulphur,  and  an  insoluble  powder  is  obtained  of 
the  formula  C,4H6S2.  Its  decomposition  by  heat  gives  rise  to 
a  variety  of  new  and  curious  products. 

754.  Chlorinized  Benzoilol,  C14H5C1O2.— This  is  obtained 
by  the  action   of  dry   chlorine  gas   upon   the  oil  of  bitter 
almonds.     It  is  a  colorless  liquid,  which  is  decomposed  by 
alkalies,  yielding  a  chlorid  and  a  benzoato.    By  distilling  this 
with  bromid  or  iodid  of  potassium,  similar  compounds  are 
obtained,  in  which  bromine  or  iodine  replaces  an  equivalent 
of  hydrogen. 

The  action  of  dry  ammonia  upon  the  chlorinized  benzoilol 
yields  hydrochloric  acid,  and  a  new  substance,  benzamide, 
Cl4lI5a02  +  NH3=CHH7NO2  +  HC\.  It  is  soluble  in  water, 
and  crystallizes  in  beautiful  prisms.  It  contains  the  elements 
of  bcnzoate  of  ammonia  minus  two  equivalents  of  water, 
and  by  the  action  of  alkalies  or  acids  takes  up  the  elements 
of  water  and  regenerates  benzoic  acid  and  ammonia,  (697.) 


BITTER    ALMOND    OIL.  389 

Hydi'obenzamide. — When  bitter  almond  oil  is  placed  in  a 
concentrated  solution  of  ammonia,  it  is  gradually  converted 
into  a  white  crystalline  mass  of  this  substance.  It  is  formed 
from  three  equivalents  of  benzoilol  and  two  of  ammonia  by 
the  abstraction  of  the  elements  of  six  equivalents  of  water, 
3(C14H6O2)  +  2NH3=C42H18N?-f6HO.  In  this  reaction  the 
ammonia  loses  the  whole  of  its  hydrogen,  which  unites  with 
the  oxygen  of  the  oil,  and  the  residue  (N2)  is  substituted  for 
O6.  By  the  action  of  hydrochloric  acid  it  takes  up  the  ele- 
ments of  water  and  regenerates  the  oil  and  ammonia ;  the 
latter  combines  with  the  acid  to  form  sal  ammoniac.  When 
boiled  in  a  solution  of  potash  it  is  converted  into  a  metameric 
modification,  which  is  no  longer  decomposed  by  acids,  but 
unites  directly  with  them,  and  neutralizes  them.  This  sub- 
stance, which  is  an  alkaloid,  is  also  formed  when  ammonia 
is  passed  through  an  alcoholic  solution  of  the  oil  of  bitter 
almonds :  it  is  called  benzoline  or  amarine. 

755.  When  bitter  almond  oil  is  exposed  to  the  air,  it  rapidly 
absorbs  oxygen,  and  is  converted  into  a  white  crystalline 
substance,  which  is  benzoic  acid :  this  is  formed  by  the  com- 
bination of  two  equivalents  of  oxygen.  The  same  effect  is 
produced  when  the  oil  is  heated  with  hydrate  of  potash : 
hydrogen  gas  is  evolved,  and  benzoate  of  potash  formed.  A 
more  abundant  source  of  benzoic  acid  is  found  in  benzoin,  a 
fragrant  resinous  substance  which  is  obtained  from  the  Laurus 
benzoin.  This  contains  a  large  quantity  of  the  acid,  which 
may  be  procured  by  exposure  to  a  gentle  heat,  when  the  acid 
is  volatilized,  and  condenses  as  a  white  sublimate.  It  is  also 
obtained  by  boiling  the  benzoin  with  lime,  which  forms  ben- 
zoate of  lime ;  hydrochloric  acid  added  to  the  previously 
concentrated  solution,  precipitates  the  pure  acid  in  crystalline 
plates.  Benzoic  acid  forms  light  silky  crystals  of  a  pearly 
whiteness,  and  has  a  pleasant  aromatic  taste,  very  slightly 
acid.  When  pure  it  is  inodorous,  but  generally  has  a  little 
volatile  oil  adhering  to  it,  which  gives  it  a  fragrant  odor,  like 
vanilla.  It  is  volatile  at  a  gentle  heat,  evolving  a  suffocating 
vapor,  which  condenses  unchanged.  It  is  very  slightly  soluble 
in  cold,  but  more  easily  in  hot  water. 

The  formula  of  benzoic  acid  is  CJ4H6O4 ;  it  is  monobasic, 
and  forms  a  large  class  of  salts,  which  are  of  but  little  im- 
portance. 

When  it  is  boiled  for  some  time  with  strong  nitric  acid, 
nitrobenzoic  acid  is  obtained.  One  equivalent  of  benzoic 
33* 


390  ORGANIC    CHEMISTRY. 

acid  and  one  of  nitric  acid  lose  the  elements  of  two  equiva- 
lents of  water,  and  the  residues  unite.  The  new  acid  is 
monobasic,  and  resembles  the  benzoic  in  its  properties. 

756.  Benzoine. — When  the  crude  oil   of  bitter  almonds 
is  mixed  with  an  alcoholic  solution  of  potash,  it  is  gradually 
converted  into  a  white  crystalline  substance,  which  is  called 
benzoine.     It  is  polymeric  of  the  oil,  and  is  formed  by  the 
union  of  two  equivalents  of  it ;  its  formula  is  consequently 
QgHuO^     When  the  vapor  of  benzoine  is  passed  through  a 
red-hot  tube,  it  is  reconverted  into  bitter  almond  oil. 

757.  Benzene. — The  vapor  of  benzoic  acid  passed  through 
a  red-hot  gun-barrel,  is  decomposed  into  carbonic  acid  and  a 
new  substance  named  benzene  or  benzole,  which   is  C]2H6 
C,4H6O4=2CO2-}-CI2H6. — Benzene  is  more  easily  obtained  by 
distilling  benzoic  acid  with  slaked  lime,  which  combines  with 
the  carbonic  acid.     It  is  a  colorless,  fragrant  liquid,  which 
boils  at  187°,  and  has  a  specific  gravity  of '830.     Benzene  is 
formed  when  the  fat  oils  are  decomposed  at  a  red  heat,  and  is 
obtained  in  the  manufacture  of  oil-gas  for  illumination. 

With  fuming  sulphuric  acid,  benzene  yields  a  coupled  acid, 
which  is  monobasic,  and  a  neutral  compound,  sulphobenzide, 
containing  the  elements  of  two  equivalents  of  benzene,  and 
one  of  sulphuric  acid,  minus  two  of  water.  The  action  of 
nitric  acid  produces  a  dense  oily  liquid  of  a  very  sweet  taste; 
it  is  nitrobenzene,  C,2H4NO4,  and  is  derived  from  one  equiva- 
lent of  benzene  and  one  of  nitric  acid,  by  the  abstraction  of 
two  equivalents  of  water.  We  may  suppose  that  two  equiv- 
alents of  hydrogen  in  the  benzene  unite  with  two  of  oxygen 
from  the  acid,  C12H6— H2  =  C12H4  and  NHO6— O2  =  NHO4. 
The  residue  of  the  acid  is  then  substituted  for  the  two  equiv- 
alents of  hydrogen  in  the  benzene,  thus,  C]2H4NHO4. 

By  the  further  action  of  fuming  nitric  acid,  a  crystalline 
compound,  named  binitrobenzene,  is  obtained.  It  is  derived 
in  the  same  manner  as  the  last,  by  the  action  of  another 
equivalent  of  the  acid,  and  has  the  formula  C12H4N2O8. 

OIL    OF    CUMIN. 

758.  The  essential  oil  of  the  seeds  of  cumin,  (Cuminum 
cyminum,)  has  the  formula   C^HjA,  and  when  heated  with 
hydrate  of  potash,  is  oxydized  with  the  evolution  of  hydrogen, 
forming  cuminate  of  potash.     The  cuminic  add,  C^HfflO4,  is 
white  and  crystalline,  resembling  the  benzoic.     Cuminol  and 


OIL    OF   SPIREA    ULMARIA.  391 

curninic  acid  are  homologues  of  benzoilol  and  the  benzole 
acid.  The  acids  in  both  instances  are  formed  by  fixing  O2, 
and  contain  four  equivalents  of  oxygen.  It  will  be  seen  that 
in  these  oils  the  difference  between  the  proportion  of  carbon 
and  hydrogen  is  the  same,  and  equals  eight  equivalents. 

OIL    OF    SPIREA    ULMARIA, 

759.  Salicylol. — This  is  obtained  when  the  flowers  of  the 
Spirea  ulmaria,  (pride  of  the  meadow,)  are  distilled  with 
water;  and  is  artificially  formed  by  the  oxydation  of  salicine, 
a   process  which  will    be   described   under   that   substance. 
Salicylol  is  a  colorless  fluid,  of  fragrant  odor,  like  the  flower 
of  the  spirea,  and  has  a  pungent  taste.     It  has  a  specific 
gravity  of  1-173,  and  boils  at  380°.     By  the  action  of  metal- 
lic oxyds  it  yields  compounds,  in  which  an  equivalent  of 
hydrogen  is  replaced  by  a  metal ;  but  in  its  other  relations  it 
does  not  resemble  an  acid.     It  does  not  pre-exist  in  the  plant 
from  which  it  is  derived,  but,  like  benzoilol,  is  formed  in  the 
process,  by  the  reaction  of  principles  not  yet  examined. 

It  absorbs  dry  chlorine  gas,  and  forms  chlorinized  sali- 
cylol,  Ci4H5ClO4 ;  bromine  and  iodine  yield  similar  com- 
pounds. Salicylol  is  metameric  with  benzoic  acid. 

By  the  action  of  ammonia  upon  an  alcoholic  solution  of  the 
oil,  hydrosalimide  is  formed.  Like  hydrobenzamide,  it  is 
derived  from  three  equivalents  of  the  oil  and  two  of  ammonia, 
by  the  abstraction  of  6HO.  Its  formula  is  C42H18N2O6 ;  it 
crystallizes  in  brilliant  yellow  prisms,  and  is  decomposed  by 
both  acids  and  alkalies,  with  the  regeneration  of  the  oil  and 
ammonia. 

760.  Salicylic  Acid,  CI4H6OC-— This  is  formed  from  the 
oil  by  the  union  of  two  equivalents  of  oxygen :  when  sali- 
cylol   is   heated  with    hydrate   of  potash,  the   salicylate   is 
formed ;  this  is  decomposed  by  hydrochloric  acid,  which  pre- 
cipitates the  salicylic  acid.     It  is  white,  crystallizable,  volatile, 
and  sparingly  soluble  in  water,  resembling  benzoic  acid.     It 
is  monobasic,  and  forms  a  large  class  of  salts,  which  are  of 
but  little  importance. 

761.  When  a  mixture  of  salicylic  acid,  sulphuric  acid,  and 
wood-spirit   are   distilled,    the   salicylic   methylic   ether   is 
obtained.     It  contains  the  elements  of  one  equivalent  of  the 
acid  and  one  of  the  spirit,  minus  two  of  water,  and   by  the 
action  of  alkalies  is  decomposed  into  a  salicylate  and  wood- 


392  ORGANIC    CHEMISTRY. 

spirit.  This  ether  is  remarkable  as  constituting  the  oil  of 
wintergreen,  Gaultheria  procumbens :  it  is  obtained  in 
large  quantities  by  distilling  the  plant  with  water.  When 
placed  in  a  close  vessel  of  strong  ammonia  it  slowly  dis- 
solves, and  the  liquid  by  evaporation  yields  wood-spirit,  and 
finally  crystals  of  salicylamide,  which  is  an  amide  of 
salicylic  acid,  and  contains  the  elements  of  salicylate  of 
ammonia  minus  two  of  water.  Like  the  other  amides,  it  is 
readily  decomposed  by  acids  and  alkalies,  by  the  action  of 
which  it  combines  with  the  elements  of  water,  and  regene- 
rates the  original  compounds.  The  mode  of  its  formation 
will  be  readily  understood  by  referring  to  what  has  been  said 
of  the  relations  between  the  ethers  and  amides,  (705.)  The 
alcohol  minus  two  equivalents  of  hydrogen,  may  be  viewed 
as  substituted  for  two  of  oxygen  in  the  acid :  the  ammonia 
gives  up  two  elements  of  hydrogen,  regenerating  the  alcohol, 
and  the  residue  takes  the  place  occupied  by  the  residue  of 
the  alcohol,  producing  an  amide  in  place  of  the  ether.  The 
ethers  of  almost  all  acids  yield  amides  in  this  way,  by  the 
action  of  ammonia. 

762.  By  the  action  of  strong  nitric  acid   upon  salicylic 
acid,  nitrosalicylic  acid   is  formed,  by  a  reaction  similar  to 
that  yielding  the  nitrobenzoic  acid,  (755.)     It  forms  white 
crystals,  very  sparingly   soluble    in   water.     When    fuming 
nitric  acid  is  gradually  added  to  the  oil  of  wintergreen,  the 
nitrosalicylic   ether   of    wood-spirit    is    obtained ;    it    forms 
delicate  yellow  crystals,  which  are  soluble  in  alcohol. 

763.  When  salicylic  acid  is  rapidly  distilled,  it  is  decom- 
posed  into    carbonic  acid   and   phenol,    C,2H6O2.C,tH6O4  — 
2CO2  +  C12HeA,.     Phenol  is   found   in  the  oil  distilled  from 
coal-tar,  and  according  to  Wohler  constitutes  the  essential  oil 
of  Castoreum,  a  secretion  of  the  beaver.     It  forms  colorless 
crystals,  which  are  liquefied  by  the  least  trace  of  moisture, 
and  is  generally  obtained  as  hn  oily  fluid,  of  a  burning  taste, 
and   pungent,  disagreeable  odor,  resembling   that  of  wood- 
smoke.     With  the  alkalies  it  forms  crystalline  compounds, 
and  has  hence  been  considered  an  acid,  and  described  by  the 
name  of  carbolic  acid.     By  the  action  of  chlorine  gas,  five 
new  products  are  obtained,  in  which  one,  two,  three,  four,  or 
five  equivalents  of  hydrogen  are  replaced  by  chlorine:  these, 
like  the  original  compound,  act  as  acids.     By  the  action  of 
nitric  acid,  phenol   yields  a  compound   in  which  two  equiv- 
alents of  nitrous  acid  are  united,  as  in  binitrobenzene,  (757.) 


OIL    OF    CINNAMON.  393 

The  final  product  of  the  action  of  nitric  acid,  is  a  substance 
in  which  the  substitution  of  the  hydrogen  is  complete,  Ci2HG 
O2+3NHO6=C123(NHO4)O2-f  6HO.  The  whole  of  the  hy- 
drogen combines  with  the  oxygen  of  the  acid,  and  is  replaced 
by  the  residue  of  the  latter.  This  substance,  which  may 
be  designated  as  tri-nitrophenol,  has  been  described  by 
different  chemists  as  nitrophenisic,  carbazotic,  nitropicric, 
and  picric  acids.  It  is  the  final  product  of  the  action  of 
nitric  acid  upon  a  great  variety  of  organic  substances ;  an 
easy  method  of  obtaining  it  is  by  boiling  salicylic  acid,  or 
oil  of  wintergreen,  with  strong  nitric  acid,  till  all  action  has 
ceased,  and  the  red  vapors  of  nitric  acid  no  longer  appear. 
The  excess  of  carbon  in  the  salicylic  acid  is  expelled  in  the 
form  of  carbonic  acid.  Nitrophenisic  acid  forms  yellowish 
white  crystalline  scales,  which  are  slightly  soluble  in  water; 
the  solution  has  a  yellow  color,  and  an  intensely  bitter 
taste.* 

Its  salts  have  a  yellow  color,  and  explode  violently  when 
heated.  The  acid  is  monobasic,  and  if  we  represent  the  acid 
by  C12H3N3O14,  its  potash  salt  will  be  C,2H2KN3OI4 ;  this  is  a 
yellow  crystalline  powder,  very  sparingly  soluble  in  water. 
Although  this  substance  and  the  other  derivatives  of  phenol 
yield  salts  with  bases,  they  appear  incapable  of  forming 
ethers  or  amides,  and  perhaps  ought  not  to  be  considered  as 
acids. 

OIL    OF    CINNAMON,  C18H9O2. 

764.  Cinnamol. — This  fragrant  oil  is  obtained  by  distilling 
the  bark  of  cinnamon  with  water.  It  is  a  heavy  fluid, 
soluble  in  water,  and  possesses  in  a  high  degree  the  taste  and 
odor  of  cinnamon.  When  exposed  to  the  air,  it  absorbs  two 
equivalents  of  oxygen,  and  is  converted  into  cinnamic  acid, 
CiSH9O4.  Cinnamate  of  potash  is  formed  with  the  evolution 
of  hydrogen,  when  cinnamol  is  heated  with  hydrate  of  pot- 
ash. This  acid  is  associated  with  the  benzoic  in  the  balsam 
of  Tolu,  and  resembles  it  in  its  properties.  When  heated 
with  nitric  acid  it  is  decomposed,  and  yields  benzoic  acid  and 
benzoilol. 

*  Whence  the  name  picric,  from  the  Greek  pifrros,  bitter. 


394-  ORGANIC    CHEMISTRY. 

SUGAR,  STARCH,  AND  ALLIED  SUBSTANCES. 

765.  Under  this  head  is  included  a  class  of  substances  of 
vegetable  origin,  which  agree  in  containing  carbon  with  oxy- 
gen   and    hydrogen    in   the  proportions  which    form    water. 
\Vhcn  soluble,  they  are  insipid  or  have  a  sweet  taste,  and  arc 
generally  nutritious.     They  are  not  volatile,  and  are  readily 
decomposed  by  heat  or  other  agents. 

766.  Sugars. — These  bodies  are  soluble  in  water,  have  a 
sweet  taste,  and  by  the  process  of  fermentation  yield  alcohol 
and  carbonic  acid. 

Cane  Sugar,  C^HnO,,. — This  occurs  in  the  juices  of 
many  plants,  as  the  sugar-cane,  maple,  beet-root,  and  Indian 
corn.  It  is  obtained  by  evaporating  the  juice  to  a  syrup, 
when  the  sugar  crystallizes  in  grains  of  a  brownish  color. 
It  is  obtained  pure  and  white  by  redissolving  it,  and  fil- 
tering the  solution  through  animal  charcoal,  (337.)  By 
the  slow  evaporation  of  a  concentrated  solution,  it  is  obtained 
in  fine  transparent  crystals,  which  are  derived  from  an  oblique 
rhombic  prism ;  in  this  state  it  constitutes  rock-candy.  It 
fuses  at  356°,  and  forms  on  cooling  a  vitreous  mass,  well 
known  as  barley  sugar;  this  gradually  becomes  opaque, 
and  changes  into  a  mass  of  small  crystals  of  ordinary  sugar. 
Sugar  is  soluble  in  about  one-third  its  weight  of  water,  form- 
ing a  thick  syrup.  It  is  insoluble  in  pure  alcohol. 

767.  Grape    Sugar;    Glucose,  C12Hj2O12  +  2Aq.  —  This 
sugar  is   found  in  the  grape  and   many  other  fruits,  and  in 
honey.     It  is  formed  when  cane  sugar  or  starch  is  boiled  with 
dilute  sulphuric  acid,  and  is  a  product  in   many  other  trans- 
formations.    The  urine  in  the  disease  called  diabetes  melli- 
tus  contains  a  large  quantity  of  grape  sugar,  which  is  formed 
from  the  starch  and  similar  substances  taken  as  food. 

Grape  sugar  is  generally  obtained  as  a  white  granular 
mass,  which  requires  one  and  a  half  parts  of  cold  water  to 
dissolve  it ;  it  is  less  sweet  to  the  taste  than  cane  sugar,  and 
about  two  and  a  half  times  as  much  are  required  to  give  an 
equal  sweetness  to  the  same  volume  of  water.  When  heated 
to '212°,  the  two  equivalents  of  water  are  expelled.  "With 
sulphuric  acid,  grape  sugar  forms  a  coupled  acid,  the  sul- 
phosaccharic.  If  a  solution  of  grape  sugar  is  mixed  with  a 
solution  of  potash,  and  then  with  a  little  sulphate  of  copper, 
the  liquid  becomes  dark,  and  soon  deposits  suboxyd  of  copper 
in  the  form  of  a  red  powder.  Cane  sugar  yields  no  precipi- 


SUGAR,  STARCH,  AND  ALLIED  SUBSTANCES.  395 

tate  until  the  solution  is  boiled.     This  test  enable  us  to  detect 
the  10Q00  part  of  grape  sugar  in  a  liquid. 

768.  Sugar  of  Milk  ;    Lactine,  CAOw+2Aq.—Th\s 
is  found  only  in  the  whey  of  milk,  and  is  obtained  by  evapo- 
rating    it,    and     purifying    the   product    by    crystallization. 
Lactine  forms   semi-transparent  prisms,  soluble  in  six  parts 
of  cold  water,  and  two  and  a   half  of  boiling  water ;  it  is 
much  less  sweet  than   cane  or  grape  sugar.     By  a  heat  of 
212°  its  water  is  expelled ;  by  boiling  with  dilute  sulphuric 
acid,  it  combines  with   the  elements  of  two  equivalents  of 
water,  and  is  converted  into  grape  sugar. 

769.  Mannite,  C6H706. — This  substance  is  not  a  proper 
sugar,  and  is  not  susceptible  of  fermentation.     It  exists  in  the 
juice  of  celery  and   many   sea-weeds ;  and  constitutes  the 
principal  part  of  the  manna  of  the  shops,  which  is  the  concen- 
trated juice  of  a  species  of  ash.     When  this   is  dissolved  in 
hot  alcohol,  the  mannite  is  deposited  by  cooling.     It  forms 
delicate  silky  crystals,  which  are  slightly  sweet  and  very 
soluble  in  water. 

Products  of  the  decomposition  of  the  Sugars. 

770.  The  vinous  fermentation. — When  the  juice  of  grapes 
or  other  fruits  containing  sugar  is  exposed  to  the  air,  a  pecu- 
liar decomposition  ensues,  in  which  the  sugar  is  resolved  into 
carbonic  acid  gas  and  alcohol.     A  solution   of  pure  sugar  is 
not  changed  by  exposure  to  the  air  ;  but  if  there  is  added  to 
it  a  little  yeast,  or  the  juice  of  any  fruit  in  the  state  of  fer- 
mentation, decomposition  takes   place,  and  carbonic  acid  and 
alcohol    are    formed.      Many  substances  besides  yeast  will 
effect  this  change,  as  blood,  albumen,  or  flour  paste  in  a  state 
of  decomposition.     It  appears  that  the  influence  of  a  ferment 
depends   on   the  condition  rather  than  the  kind  of  matter. 
Any  nitrogenized  substance  capable  of  undergoing  putrefac- 
tion produces  the  same  effect,  and  we  are  to  attribute  this 
change,  in  the  juice  of  fruits,  to  a   small  portion  of  albumi- 
nous matter  present.     The  mode  in  which   these  substances 
act  is  not  understood,  but  it  is  supposed  that  when  in  a  state 
of  decomposition,  they  are  able  to  induce  a  similar  state  in 
ether  substances  with  which  they  are  in  contact ;  the  equili- 
brium of  the  atoms  in  the  compound   is  thus  disturbed,  and 
the  elements  arrange  themselves  in  new  forms. 

771.  The  conversion  of  grape  sugar  into  alcohol  and  car- 
bonic acid  is  very  simple ;  one  equivalent  of  dry  grape  sugar, 


396  ORGANIC    CHEMISTRY. 


contains  the  elements  of  two  equivalents  of  alcohol 
and  four  of  carbonic  acid  gas  : 

2  equivalents  of  alcohol,  2  X  (C4H602)  =  C8Hi204 

4          «  "   carbonic  acid  gas,  4  X  CO2  =  C4       O8 


I          "  «  grape  sugar, 

Grape  sugar  is  the  only  kind  which  is  capable  of  this  fer- 
mentation ;  and  although  the  others  readily  yield  alcohol 
and  carbonic  acid,  it  is  found  that  the  first  effect  of  the  fer- 
ment is  to  transform  them  into  grape  sugar  by  the  assimila- 
tion of  the  elements  of  water. 

Many  juices  of  fruits  readily  become  sour  by  exposure  to 
the  air,  especially  if  the  quantity  of  sugar  which  they  con- 
tain, and  consequently  the  portion  of  alcohol  that  can  be 
formed,  is  small.  But  in  these  cases,  the  formation  of  the 
acid,  which  is  the  acetic,  is  probably  preceded  by  that  of 
alcohol. 

772.  When  sugar  is  mixed  with  caseine  (cheese  curd)  and 
exposed  to  a  temperature  of  from  95°  to  104°,  a  peculiar  fer- 
mentation takes  place,  which  produces  a  slimy  substance  that 
renders  the  liquid  viscid.     The  other  products  are  mannite 
and  lactic  acid,  C6H6O6.     The  gummy  matter  is  identical  in 
composition  with  sugar. 

Similar  products  are  obtained  when  the  juices  of  beets  and 
carrots  ferment  at  a  high  temperature.  This  has  been  termed 
the  viscous  fermentation.  When  caseine  or  any  other  animal 
matter  in  an  advanced  state  of  decomposition  is  employed,  it 
induces  the  alcoholic  fermentation  ;  but  at  an  earlier  stage  of 
the  decay  the  action  is  different,  giving  rise  to  lactic  acid  and 
mannite. 

When  milk  is  exposed  to  a  temperature  from  95°  to  104°, 
it  undergoes  the  vinous  fermentation,  and  forms  alcohol.  It 
is  well  known  that  some  nations  prepare  an  intoxicating 
liquor  by  the  fermentation  of  milk.  In  this  process,  a  small 
quantity  of  acid  is  first  formed,  which  converts  the  lactine 
into  grape  sugar.  The  elevated  temperature  promotes  the 
decomposition  of  the  caseine  present,  and  thus  enables  it  to 
produce  this  fermentation.  Milk  at  ordinary  temperatures 
becomes  directly  acid,  without  the  previous  formation  of 
alcohol,  and  its  sugar  is  then  transformed  into  lactic  acid. 

773.  Lactic  Acid,  C6H6O6.  —  This  acid  may  be  obtained 
from  sour  milk,  but  is  more  easily  prepared  by  thg  fermenta- 
tion of  sugar  with  caseine.     Fourteen  parts  of  cane  sugar 


SUGAR,  STARCH,  AND   ALLIED   SUBSTANCES.  397 

tire  dissolved  in  sixty  of  water ;  to  the  solution  is  then  added 
four  parts  of  the  curd  from  milk,  and  five  parts  of  chalk  to 
neutralize  the  acid  which  is  formed.  This  mixture  is  kept 
at  a  temperature  of  77°  to  86°  F.  for  two  or  three  weeks,  or 
until  it  becomes  a  crystalline  paste  of  lactate  of  lime.  This 
is  pressed  in  a  cloth,  dissolved  in  hot  water,  and  filtered;  the 
solution  is  then  concentrated  by  evaporation.  On  cooling,  it 
deposits  the  salt  in  crystals,  which  may  be  purified  by  re- 
crystallization.  This  process  yields  about  thirteen  and  a 
half  parts  of  the  crystallized  lactate,  and  a  small  quantity 
of  mannite.  The  reaction  is  very  simple ;  one  equivalent 
of  dry  grape  sugar,  C12HI2O,2,  contains  the  elements  of  two 
equivalents  of  lactic  acid,  2(C6H6O6.)  The  mannite  is  the 
result  of  a  secondary  decomposition,  and  with  certain  pre- 
cautions, lactic  acid  is  the  only  product.  The  carbonate  of 
lime  serves  only  to  neutralize  the  acid  formed.  The  lactate 
of  lime  may  be  decomposed  by  the  careful  addition  of  oxalic 
acid,  which  precipitates  the  lime,  and  the  solution  of  lactic 
acid  thus  obtained,  is  concentrated  by  evaporation,  and  purified 
by  solution  in  ether.  It  is  a  syrupy  liquid,  of  specific  gravity 
1*215,  and  is  strongly  acid  to  the  taste. 

774.  When  lactic  acid  is  heated  to  482°,  a  white  crystal- 
line substance  sublimes  which  is  called  lactide  ;  it  is  derived 
from  the  acid  by  the  abstraction  of  the  elements  of  two  equi- 
valents of  water,  and  has  the  formula  C6H4O4.     It  is  soluble 
in  alcohol,  but  scarcely  soluble  in  water ;  by  long  continued 
boiling  with  it,  however,  it  is  converted  into  lactic  acid.    This 
acid  is  monobasic,  and  its  salts  are  generally  soluble  and 
crystallizable.     The  lactate  of  lime  (C6H5CaO6)  crystallizes 
in  fine  prisms,  with  five  equivalents  of  water.     The  lactate 
of  zinc  is  obtained  by  decomposing  a  hot  concentrated  solu- 
tion of  lactate  of  lime  by  chlorid  of  zinc;  the  salt  crystallizes 
in  cooling  in  beautiful  colorless  prisms.     The  lactate  of  iron 
(C6H5FeO6)  is  sparingly  soluble  in  cold  water,  and  may  be 
prepared  by  a  similar  process ;  it  is  employed  in  medicine. 

775.  When  the  mixture  of  sugar,  chalk,  and  curd  is  kept 
at  a  higher  temperature,  about  90°,  a  different  action   takes 
place ;    hydrogen  gas  is  evolved,  and   butyrate  of  lime  is 
formed.     This  product  will  be  afterwards  described. 

The  action  of  chromic  acid  upon  sugar  yields  formic  acid, 
(740.)     Dilute  nitric  acid  forms,  with  cane  and  grape  sugar, 
saccharic  acid,  C,2H,0O14 ;  it  is  bibasic ;  strong  nitric  acid 
converts  them  into  oxalic  acid. 
34 


398  ORGANIC    CHEMISTRY. 

776.  When  sugar  is  added  to  a  concentrated  solution  of 
three  times  its  weight  of  hydrate  of  potash  and  heated,  the 
mixture  becomes  brown,  and  hydrogen  gas  is  evolved.    When 
the  action  ceases,  and  the  mass  is  cooled,  dissolved  in  water, 
and  distilled  with  dilute  sulphuric  acid,  it  yields  formic  and 
acetic   acids,  with   a  new  acid,  the  metacetonic,  which    is 
obtained  as  a  volatile  liquid,  with  a  pungent  acid  odor.     It  is 
monobasic,  and  has  the  formula   CgHgO., :  it  is  therefore  a 
homologue  of  formic  and  acetic  acids. 

A  mixture  of  sugar  and  quick  lime  when  distilled  affords 
acetone,  and  an  oily  liquid  called  metacc.tone  :  this  is  related 
to  the  metacetonic  acid  as  acetone  is  to  the  acetic,  and  yields 
that  acid  when  distilled  with  a  mixture  of  bichromate  of 
potash  and  sulphuric  acid.  Mannite,  starch,  and  gum,  afford 
the  same  results  with  hydrate  of  potash  and  lime. 

777.  Gum,  C12H10O|0. — This  substance  is   best  known  in 
gum  arable ;  the  gum  which  exudes  from  the  cherry  and 
plum,  the  mucilage  of  flaxseed,  and   many  other  plants,  are 
identical  with  it.      Gum   is  soluble  in  water,  and  forms  a 
viscid  solution,  from  which  alcohol  precipitates  it  unchanged. 

When  boiled  with  dilute  sulphuric  acid,  it  is  converted 
into  grape  sugar.  With  nitric  acid,  gum  and  milk  sugar 
yield  the  mucic  acid,  which  distinguishes  them  from  all 
the  other  bodies  of  this  class.  The  mucic  acid  is  a  white 
crystalline  powder,  which  is  sparingly  soluble  in  water;  it  is 
bibasic,  and  is  represented  by  the  formula  C,2H10O,6.  It  is 
consequently  metameric  with  the  saccharic  acid,  although 
quite  different  in  its  properties. 

778.  The    Pectic  Acid,  which   is  extracted   from   many 
fruits,  appears  to   be  nothing  but  a  modified   form  of  gum, 
and  yields   grape  sugar  with  dilute  acids.     It  combines  with 
lime  and   some  other  bases  to  form  compounds,  which   have 
been  described  as  pectates.     Both  gum  and  sugar  have  also 
the  property  of  exchanging  one  or  two  equivalents  of  hy- 
drogen  for   lead,  barium,  or  calcium,  to   form   similar  com- 
binations. 

779.  Starch,  C,2H10O10. — This  substance  exists  in  a  great 
variety  of  vegetables.     It  is  found  in  all   the  cereal   grains, 
in  the  roots  and   tubers  of  many  plants,  as  the  potato,  and 
in  the  bark  and   pith  of  various   trees.     It   is   obtained   by 
bruising  wheat  and  washing  it  in  cold  water,  which  holds  the 
starch  in   suspension,  and  deposits  it  on  standing.     Potatoes 
furnish  a  large  portion  of  starch  by  a  similar  process.     The 


SUGAR,  STARCH,  AND    ALLIED    SUBSTANCES. 


399 


substances  known  as  arrow-root,  sa- 
lep,  sago,  and  tapioca,  are  varieties 
of  starch,  obtained*  from  different 
plants,  and  sometimes  altered  by  the 
heat  employed  in  drying. 

When  examined  by  the  naked  eye 
it  is  a  white  shining  powder,  but  under 
the  microscope  is  seen  to  consist  of 
irregular  grains,  which  have  a  rounded 
outline,  and  are  composed  of  concentric 
layers,  covered  with  an  external  mem- 
brane. The  diameter  of  the  grains  of 
potato  starch  is  about  ¥^g-  of  an  inch. 

Starch  is  insoluble  in  cold  water,  but  if  the  mixture  is 
heated,  the  globules  swell,  burst  their  envelopes,  and  form  a 
transparent  jelly,  which  is  characterized  by  producing  a 
deep-blue  color  with  a  solution  of  iodine. 

When  the  solution  of  starch  is  mixed  with  a  little  acid  or 
an  infusion  of  malt,  and  gently  heated,  it  becomes  very  fluid, 
and  is  changed  into  dextrine*  This  has  the  same  com- 
position as  starch,  but  is  very  soluble  in  cold  water,  and  is 
not  colored  blue  by  iodine.  If  starch  is  heated  to  300°  or 
400°,  it  is  rendered  soluble  in  water,  and  possesses  all  the 
properties  of  dextrine.  In  this  state  it  is  used  in  the  arts  as 
a  substitute  for  gum,  under  the  names  of  British  Gum  and 
leiocome.  When  dextrine  is  boiled  for  some  time  with 
dilute  sulphuric  acid,  it  is  converted  into  grape  sugar. 
It  has  been  mentioned  that  grape  sugar  is  formed  in  this  way 
from  starch ;  but  its  formation  is  always  preceded  by  that 
of  dextrine.  One  part  of  starch  may  be  dissolved  in  four 
parts  of  water,  with  about  one-twentieth  of  sulphuric  acid, 
and  the  mixture  boiled  for  thirty-six  or  forty  hours.  The 
liquid  is  then  mixed  with  chalk  to  separate  the  acid,  and  by 
evaporation  and  cooling  affords  pure  grape  sugar.  Oxalic 
acid  may  be  substituted  for  the  sulphuric,  with  the  same 
result.  Starch  sugar  is  extensively  manufactured  in  Europe, 
and  is  often  used  to  adulterate  cane  sugar.  In  this  process 
the  starch  combines  with  the  elements  of  two  equivalents  of 
water,  C12H100 10  + 2HO=C12H,2Oi2;  the  acid  is  obtained  at 


*  So  named,  because  when  a  beam  of  polarized  light  is  passed 
through  the  solution,  it  causes  the  plane  of  polarization  to  deviate 
to  the  right  hand. 


400  ORGANIC    CHEMISTRY. 

the  end  of  the  process  quite  unaltered,  and  one  part  of  acid 
will  saccharify  one  hundred  of  starch,  by  long  continued 
boiling.  Starch  or  dextrine  unites  with  sulphuric  acid  to 
form  a  coupled  acid ;  and  it  is  probable  that  this  is  first 
formed,  and  then  destroyed  by  boiling :  at  the  moment  of 
decomposition,  the  liberated  dextrine  takes  up  the  elements 
of  water  necessary  for  the  formation  of  sugar.  A  small 
portion  of  the  coupled  acid  is  always  found  in  the  solution. 

780.  The  action  of  an  infusion  of  malt   upon   sugar  is 
peculiar ;    this    substance    is    prepared    from    barley,    by 
moistening  the  grain  with  water,  and  exposing  it  to  a  gentle 
heat  till  germination  takes  place,  when  it  is  dried  in  an  oven 
at  such  a  temperature  as  to  destroy  its  vitality.     The  grain 
now  contains  a  portion  of  starch  sugar,  and  'a  small  portion 
of    a    substance    called   diastase,*    to    which    its    peculiar 
properties  are  due.     It  is  precipitated   by  alcohol    from  a 
concentrated   infusion  of  malt,  as  a  white  flaky  substance, 
which  contains  nitrogen,  and  is  very  prone  to  decomposition. 
When  a  little  diastase   is  added  to  a  mixture  of  starch  and 
water,  at  a  temperature  of  from  130°  to  140°,  the  starch  is 
soon  converted  into  dextrine,  and  in  a  few  hours  into  grapo 
sugar.     The  action  of  an  infusion  of  malt  is  due  solely  to  the 
presence  of  a  minute  portion  of  this  substance,  one  part  of 
which  will  convert  two  thousand  parts  of  starch  into  sugar. 
This  effect  appears  to  be  due  to  a  peculiar   state  of  the 
diastase,  which   is  a  portion  of  the  azotized   matter  of  the 
grain  in  a  modified  form,  and  is  analogous  to  that  of  ferments, 
already  alluded  to. 

781.  Woody    Fibre;    Cellulose,  C12H10O10.  —  This   sub- 
stance is  the  solid  insoluble  part  of  vegetables,  and  remains 
when  water,  alcohol,  ether,  dilute  acids  and  alkalies,  have 
extracted   from  wood  all  its  soluble  portions.     It  is  nearly 
pure  in  paper  or  old   linen.     Cellulose  is  identical  in  com- 
position with  starch  and  dextrine,  and  by  the  action  of  strong 
sulphuric  acid  is  dissolved  and  converted  into  that  substance. 
This  experiment  is  easily  made  with  unsized  paper  or  cotton  ; 
to  two  parts  of  this,  one  part  of  the  acid  is  very  slowly  added, 
taking  care  to  prevent  an  elevation  of  temperature,  which 
would   char  the   mixture.      In  a  few    hours  the  whole   is 
converted  into  a  soft  mass,  which  is  soluble  in  water,  and  is 

*  From  the  Greek  diistemi,,  to  separate,  because  it  separates  the 
insoluble  envelopes  of  the  starch  globules. 


SUGAR,  STARCH,  AND  ALLIED  SUBSTANCES.      401 

principally  dextrine.  If  the  mixture  is  now  diluted  with 
water  and  boiled  for  three  or  four  hours,  the  dextrine  is  com- 
pletely converted  into  grape  sugar,  which  is  obtained  by 
neutralizing  the  acid  with  chalk,  and  evaporation.  By  this 
process  paper  or  rags  will  yield  more  than  their  weight  of 
crystallizable  sugar. 

782.  The   mutual   convertibility   of   these   different   sub- 
stances is  interesting  in  relation  to  many  of  the   phenomena 
of  vegetable  life.     The  starch  in   the  germinating  seed   is 
changed    by   the    action   of  diastase   into   sugar,    in    which 
soluble  form  it  seems  better  fitted  for  the  nourishment  of  the 
embryo  plant.     In  the  growth  of  this,  we  have  an  example 
of  the   formation   of  cellulose    from    sugar,    in   which   this 
substance  assumes  a  structural  form  under  the  action  of  the 
vital  force.     This  is  a  transformation  from  the  unorganized 
to  the  organized,  which  mere  chemical  affinity  can  never 
effect. 

783.  Many  unripe   fruits,  as  the  apple,  contain  a  large 
quantity  of  starch,  but  no  sugar.     After  the  fruit  is  fully 
grown,  the  starch  gradually  disappears,  and  in  its  place  we 
find   grape  sugar.     This  change  constitutes  the  ripening  of 
fruits,  and  as  it  is  well  known,  will  take  place  after  they  are 
gathered.     In   this  process  we  have  clearly  a  conversion  of 
the  starch  into  sugar,  by  the  agency  of  the  vegetable  acids 
present   in   the  fruit,  a  change  which   is   the   reverse  of  the 
previous  one,  and  is  probably  independent  of  life. 

784.  Xyloidine ;  Gun  Cotton. — When   starch  is   rubbed 
in  a  mortar  with  nitric  acid  of  specific  gravity  1'5,  it  forms 
a  gelatinous  mass  from  which  water  precipitates  xyloidine. 
When  dry,  it  is  a  white  powder,  which  takes  fire  at  a  low 
temperature  and  burns  with  great  vivacity.     Its  composition 
is  C12H9NOi4,  and  it  is  derived  from   starch,  by  the  addition 
of  one  equivalent   of  nitric  acid  and  the  abstraction  of  the 
elements  of  two  of  water,  C12H10O10  +  NHO6  =  C12H9NO14 
+  2HO.     The  nitric  acid  less  O2  may  be  viewed   as   repre- 
senting H2  in  the   starch,  and  we  may  write  the   formula 
C12H8(NH04)010,  (675.) 

The  action  of  strong  nitric  acid  upon  woody  fibre  gives 
origin  to  another  substance,  which  has  lately  attracted  great 
attention  as  a  substitute  for  gunpowder,  under  the  name  of 
gun  cotton,  and  which  Mr.  Pelouze  has  called  pyroxyline. 
Paper,  saw-dust,  or  any  other  form  of  cellulose,  by  digestion 
in  strong  nitric  acid,  acquires  a  considerable  increase  of 
34* 


402  ORGANIC    CHEMISTRY. 

weight,  and  is  converted  into  this  new  substance ;  but  it  is 
best  obtained  from  cotton.  The  following  is  an  outline  of 
the  process :  one  hundred  grains  of  clean  cotton  are  im- 
mersed for  five  minutes  in  a  mixture  of  an  ounce  and  a  half 
of  nitric  acid  of  specific  gravity  1*45  to  1-5,  with  the  same 
measure  of  strong  sulphuric  acid ;  it  is  then  removed,  care- 
fully washed  in  cold  water  from  every  trace  of  acid,  and 
dried  at  a  temperature  which  should  not  exceed  120°.  As 
thus  prepared  it  preserves  the  form  of  the  cotton  unaltered, 
hut  has  less  strength  than  the  original  fibre.  It  inflames  by 
a  very  gentle  heat ;  sometimes  under  circumstances  not 
well  understood,  it  has  been  observed  to  take  fire  at  212°  F. 
Its  combustion  is  instantaneous,  accompanied  by  an  immense 
volume  of  flame,  and  it  leaves  not  the  slightest  residue. 
When  ignited  in  a  confined  space,  it  explodes  with  great 
violence :  one-tenth  of  a  grain  is  sufficient  to  shatter  the 
strongest  glass  tube.  Its  power  in  propelling  balls  is  about 
eight  times  greater  than  that  of  gunpowder.  Its  tremendous 
energy  depends  upon  the  fact  that  it  is  completely  resolved, 
by  its  combustion,  into  aqueous  vapor  and  permanent  gases, 
which  are  carbonic  oxyd,  carbonic  acid,  and  nitrogen.  As 
these  are  much  less  noxious  than  the  gases  resulting  from 
the  combustion  of  gunpowder,  the  gun  cotton  will  be  found 
of  great  use  in  mining.  Its  analysis  is  very  difficult,  on 
account  of  its  explosiveness ;  but  from  the  results  of  Pelouze 
and  others,  it  appears  to  be  derived  from  two  equivalents  of 
cellulose  and  five  of  nitric  acid,  with  the  abstraction  of  ten 
of  water:  2C12H10O10  =  C^A,,  +  5NHO6  =  C24H15NA0-f 
10HO.  There  are  reasons  for  supposing  that  the  equivalent 
of  cellulose  and  all  the  allied  substances  should  be  doubled, 
and  this  substance  will  then  be  cellulose,  CajfLjoO^,  in  which 
the  residue  of  five  equivalents  of  nitric  acid  replaces  ten  of 
hydrogen,  which  have  formed  water  with  the  oxygen  of  the 
acid.  Its  formula  may  then  be  written  C^H^NHO^O^. 
This  formula  requires  that  100  parts  of  cellulose  should 
yield  169-1  of  pyroxyline,  and  experiment  gives  170  to  172 
parts.  It  is  very  difficult  to  dry  it  perfectly,  for  it  is  gradually 
decomposed  at  212°,  and  often  explodes  at  that  temperature  : 
hence  the  analyses  have  invariably  given  a  little  more 
oxygen  and  hydrogen  than  the  formula  requires.  Pyroxy- 
line, when  pure,  is  soluble  in  the  acetic  ethers  of  alcohol  and 
wood-spirit. 


SUGAR,  STARCH,   AXD    ALLIED   SUBSTANCES.  403 

Transformation  of  Woody  Fibre. 

785.  Byjhe  action  of  atmospheric  air  and  moisture,  wood 
undergoes  a  slow  decay,  dependent  on  the  absorption  of  oxy- 
gen, to  which  Liebig  has  applied    the   term   eremacausis.* 
The  carbon  is  converted  into  carbonic  acid,  while  the  oxygen 
and  hydrogen  of  the  lignine  unite  to  form  water.     The  resi- 
due is  still  found  to  contain  oxygen   and  hydrogen  in  the 
original    proportions,  but   the   relative  amount  of  carbon  is 
continually    increasing.     For   each   equivalent   of  carbonic 
acid  two  of  water  are  evolved.     The  final  result  of  this  pro- 
cess is  a  brown  or  black  residue,  which  constitutes  vegetable 
mould.     Different  products  of  this   decomposition   have  been 
described  under  the  names  of  humus,  geine,  ulmine,  humic 
and  ulmic  acids. 

Nearly  all  of  these  bodies  contain  ammonia,  for  which 
they  have  a  strong  affinity  ;  this  is  in  part  absorbed  from  the 
air,  but  the  late  experiments  of  Mulder  have  shown  that  they 
have  the  power  of  forming  ammonia  from  the  nitrogen  of 
the  atmosphere.  Pure  humic  acid  moistened  and  placed  in  a 
close  vessel  filled  with  air,  is  found  after  some  months  to 
contain  a  considerable  quantity  of  ammonia.  The  hydrogen 
evolved  by  a  slow  decomposition  of  the  water,  is  brought  into 
contact  with  nitrogen  under  such  conditions,  that  they  com- 
bine and  produce  the  alkali. 

786.  The   decomposition   of  wood,   when  buried   in   the 
ground  and  excluded  from  the  action  of  the  air,  is  very  dif- 
ferent.    The  oxygen  which  it  contains,  gradually  combines 
with  the  carbon   to  form  carbonic  acid,  and   substances  are 
obtained,  in  which  the  proportion  of  carbon  and  hydrogen  is 
greater  than  in  the  original  fibre.     Peat,  lignite,  and  bitu- 
minous coal,  are  products  of  this  decomposition.     The  car- 
bon and  hydrogen  in  coal  combine  in  various  ways,  and  often 
generate  vast  quantities   of  gaseous  carburets  of  hydrogen, 
(450.)     Anthracite  has  resulted  from  the  action  of  heat  on 
bituminous  coal,  which  has  expelled  all  the  volatile  ingre- 
dients, and  left  a  residue  of  nearly  pure  carbon. 

Destructive  Distillation  of  Wood. 
The  principal  products  of  the  decomposition  of  wood  by 

*  From  erema,  slow,  and  Jcausis,  combustion,  a  term  by  which 
that  chemist  denotes  those  changes  which  take  place  in  organic 
bodies  from  the  gradual  action  of  oxygen. 


404  ORGANIC    CHEMISTRY. 

heat,  are  acetic  acid  and  pyroxylic  spirits,  and  have  been 
already  described,  (720,  734).  Beside  these  a  quantity  of 
viscid  tarry  matter  is  obtained,  which  contains  *nany  very 
interesting  compounds. 

787.  Kreasote. — This  substance  occurs  dissolved  in   the 
crude  acetic   acid   from  wood,  and   is  separated  and  purified 
by  a  complicated  process.     It  is  a  colorless  oily  fluid,  which 
boils  at  397°,  and  has   a  specific  gravity  of  1-037  ;  it  has  a 
peculiar  and  very  persistent  odor  resembling  that  of  smoke, 
and  a  powerful  burning  taste.     It  is  soluble  in  about  100  parts 
of   water,    and    the   solution    possesses   powerful   antiseptic 
qualities.     Meat  which  has  been  soaked  in  it,  is  incapable  of 
putrefaction,*    and    acquires   a   delicate    flavor   of    smoke. 
The  power  of  wood  smoke  to  preserve  flesh,  is  due  to  the 
presence  of  kreasote.     It  is  a  corrosive  poison  when  taken  in 
any  quantity,  but  a   little  dilute  solution  is  used  medicinally, 
both  internally  and  externally,  as  a  styptic  and  antiseptic.     It 
is  often  applied  to  the  nerve  of  a  decayed  tooth,  and  in  this 
may  relieve  the  pain  of  tooth-ache,  but  its  use  requires  care, 
for  if  brought  in  contact  with  the  lining   membrane  of  the 
mouth,  it  instantly  destroys  its  vitality. 

788.  The   composition    of  kreasote   is    C,4H8O2 ;    by  the 
action  of  nitric,  it  yields  nitrophenisic  acid,  (763).     It  com- 
bines with  the  alkalies  to  form  crystalline  compounds. 

Wood-tar  contains  several  carburets  of  hydrogen,  one  of 
which,  called  eupione,  is  an  oily,  fragrant  liquid,  of  the 
specific  gravity  -655,  being  the  lightest  liquid  known.  Its 
formula  is,  probably,  C6H6. 

Paraffinc.  —  This  is  a  white  crystalline  substance,  ob- 
tained from  the  less  volatile  portions  of  wood-tar.  It  crys- 
tallizes in  delicate  needles,  which  fuse  at  110°;  it  is  soluble 
in  alcohol  and  ether.  Its  formula  is  C48H50.  Paraffine  is 
obtained  in  large  quantities  by  the  dry  distillation  of  bees- 
wax. 

789.  Coal    Tar    consists    principally    of   a    mixture   of 
various  hydrocarbons  ;  some  of  these  are  liquids  and  quite 
volatile,  constituting  what  is  called  gas  naphtha.     Among  the 
less  volatile  products,  are  two  solid  carburets  of  hydrogen, 
naphthalene,  and  paranaphthalene,  or  anthracene.     The  first 
of  these  is  formed  by  the  decomposition   of  many  organic 
matters  by   heat.     Its   formula  is  C^Hg ;  ft  is  volatile,  and 


*  Hence  the  name,  from  the  Greek  kreas,  flesh,  and  soto,  I  preserve. 


FATS  AND  THE  SUBSTANCES  DERIVED  THEREFROM.        405 

forms  beautiful  pearly  crystals  of  a  fragrant  odor.  The 
action  of  chlorine,  bromine,  and  nitric  acid  on  naphthaline, 
gives  rise  to  a  great  number  of  compounds,  which  have  lately 
been  studied  by  Laurent.  They  are  formed  by  successive 
substitutions  of  the  hydrogen  by  one  or  more  of  these  sub- 
stances, and  many  metameric  modifications  of  these  bodies 
exist.  Thus,  the  bichlorinized  naphthaline,  C20H6C12,  occurs 
in  seven  modifications,  which  are  perfectly  distinct  in  their 
characters.  We  are  forced  to  suppose  that  these  compounds 
owe  their  different  properties  to  a  different  arrangement  of 
their  constituent  atoms,  and  it  is  easy  to  see  that,  in  this 
way,  the  number  of  possible  combinations  will  be  immense. 
More  than  twenty  substances  have  been  described,  in  which 
chlorine  is  in  part  substituted  for  the  hydrogen  of  the  naph- 
thaline. The  final  product  of  the  action  of  chlorine  is 
CaoClg,  being  a  chlorid  of  carbon,  which  preserves  the  type 
of  naphthaline.  In  addition  to  these,  coal-tar  contains  a  con- 
siderable proportion  of  phenol  or  carbolic  acid,  (763)  and 
two  organic  alkaloids,  named  Icyanol  and  leukol.  The 
watery  products  of  the  distillation  of  coal  hold  a  large 
quantity  of  ammonia  in  solution,  often  combined  with  hydro- 
sulphuric  and  hydrocyanic  acids. 

790.  Petroleum. — In  many  parts  of  the  world,  an  oily 
matter  exudes  from  the  rocks,  or  floats  on  the  surface  of 
springs.    The  principal  sources  of  this  substance  are  Amiano 
in  Italy,  Ava,  and  Persia,  but  it  is  found  in  many  places  in 
our  own  country.     The  well  known  Seneca  Oil  is  an  in- 
stance of  this  kind.     Petroleum  is   a  variable  mixture  of 
several   bodies.     By  distillation,  it  yields  a  colorless  liquid 
called  naphtha,  which  is  very  light,  volatile,  and  combustible. 
Its  formula  is  C6H5.    Naphtha  occurs  nearly  pure  in  Italy  and 
Persia,  and  is  used  for  illumination. 

Petroleum  contains  a  variety  of  other  bodies,  among  which 
are  paraffi?ie,  and  several  resinous  matters,  formed  perhaps 
by  the  oxydation  of  naphtha.  These  substances  are  probably 
derived  from  coal  or  other  matters  of  vegetable  origin. 

FATS    AND    THE    SUBSTANCES    DERIVED    FROM    THEM. 

Glycerides. 

791.  Under  the  general  name  of  fats  is  included  a  large 
class  of  bodies  of  animal  and  vegetable  origin,  which  are 
characterized  by  being  insoluble  in  water,  combustible,  and 


406  ORGANIC    CHEMISTRY. 

volatile  only  at  high  temperatures  with  decomposition.  Some 
of  them,  as  the  oils,  are  liquid  at  common  temperatures, 
while  others,  as  mutton  tallow,  require  a  heat  of  120°  for 
their  fusion.  When  digested  with  water  and  an  alkali,  or  a 
basic  metallic  oxyd,  they  take  up  the  elements  of  water,  and 
are  resolved  into  acids,  which  unite  with  the  base,  forming 
the  compounds  called  soaps,  and  a  peculiar  sweet  substance 
to  which  the  name  of  glycerine*  is  given. 

Glycerine  is  most  easily  prepared  by  heating  a  mixture  of 
olive  oil,  oxyd  of  lead,  and  water.  The  oil  is  decomposed, 
and  the  acids  form  insoluble  salts  with  the  lead,  while  the 
glycerine  is  dissolved  in  the  water;  the  solution  is  treated 
with  sulphureted  hydrogen  to  precipitate  a  little  dissolved 
oxyd  of  lead,  and  evaporated  in  a  water-bath.  The  formula 
of  glycerine  is  C6H8O6.  It  is  a  colorless,  syrupy  liquid,  of  a 
very  sweet  taste,  and  is  readily  soluble  in  water  and  alcohol , 
it  is  not  volatile,  but  when  strongly  heated  is  decomposed, 
evolving  acetic  acid,  and  other  products,  the  most  important 
of  which  is  acroleine.  This  is  obtained  pure  by  distilling 
glycerine  with  anhydrous  phosphoric  acid;  it  is  formed  from 
it  by  the  abstraction  of  the  elements  of  four  equivalents  of 
water,  C6H8O6  —  4HO=C6H4O2,  the  formula  for  acroleine. 
It  is  a  colorless  liquid,  having  a  powerful  pungent  odor, 
which  irritates  the  eyes  and  nose  exceedingly,  and  is  the 
same  smell  that  is  evolved  when  fats  are  strongly  heated. 
With  sulphuric  acid  glycerine  yields  a  coupled  acid. 

792.  All  of  the  fats  contain  the  elements  of  one  equivalent 
of  glycerine,  and  two  of  an  acid  minus  six  equivalents  of 
water.     For  example :    palmitine  yields,   by  the  action   of 
alkalies,  ethalic  acid  and  glycerine,  and  its  composition  may 
be  expressed  by  (C6H8O6  +  2C32H3204)-6HO-C70H66O8.     In 
its  decomposition  it  takes  up  the  elements  of  six  equivalents  of 
water,  and  regenerates  glycerine  and  the  acids.     These  sub- 
stances present  some  analogy  to  the  ethers,  (702,)  and  amides, 
(697,)  in  their  mode  of  decomposition  ;  they  are  distinguished 
by  the  general  name  of  glycerides.    None  of  these  are  volatile 
without  decomposition ;  when  distilled  they  yield  some  com- 
pound of  carbon  and  hydrogen,  a  fatty  acid,  and  acroleine ; 
the  peculiar  pungent  odor  of  this  last  is  characteristic  of  the 
glycerides. 

793.  The  ethalic  acid,  which  results  from  the  decomposi- 
tion of  palmitine,  has  been  already  noticed  as  a  derivative  of 

*  From  the  Greek  gliikus>  sweet. 


FATS  AND  THE  SUBSTANCES  DERIVED  THEREFROM.        407 

one  of  the  alcohols,  and  phocenine,  another  glyceride,  yields, 
by  its  saponification,  valerianic  acid,  which  is  a  product  of 
the  oxydation  of  amylic  alcohol.  There  are  in  addition  to 
these  a  large  number  of  fatty  acids  derived  from  the  saponi- 
fication of  glycerides,  which  are  homologues  of  valerianic 
and  ethalic  acids,  and  these  being  the  most  important,  will  be 
first  described. 

794.  Butyric  Acid,  C8H8O4. —  Butter  is  a  mixture  of 
several  glycerides :  the  one  to  which  it  owes  its  agreeable 
flavor  is  called  butyrine,  and  when  saponified  by  an  alkali 
yields  butyric  acid.  It  has  been  recently  discovered  that  the 
fermentation  of  sugar  under  peculiar  circumstances  produces 
butyric  acid,  a  fact  referred  to  when  describing  sugar.  A 
solution  of  sugar  is  mixed  with  a  little  curd  of  milk,  and  a 
sufficient  quantity  of  chalk  to  saturate  the  acid  which  will 
afterwards  be  formed.  The  mixture  is  placed  in  a  situation 
where  the  temperature  is  from  77°  to  86°  F. :  the  fermenta- 
tion is  at  first  viscous,  then  lactic,  and  finally  butyric :  much 
hydrogen  and  carbonic  acid  gases  are  evolved,  and  the  mix- 
ture emits  a  very  unpleasant  odor.  After  several  weeks  the 
evolution  of  gas  ceases,  and  the  liquid  contains  nothing  but 
butyrate  of  lime.  The  operation  succeeds  best  when  con- 
siderable quantities  are  employed.  The  reaction  is  very 
simple.  The  sugar  is  probably  first  converted  into  grape  sugar, 
one  equivalent  of  which,  C,2H,2O12:=C8H8O4  +  4CO2  +  H4. 

This  acid  is  easily  procured  by  distilling  the  butyrate  of 
lime  with  hydrochloric  acid ;  it  must  be  digested  with  chlorid 
of  calcium,  and  redistilled  to  obtain  it  free  from  water.  Pure 
butyric  acid  is  a  limpid  colorless  liquid,  which  is  dissolved  in 
all  proportions  by  water  and  alcohol,  boils  at  327°,  and  has 
a  specific  gravity  of  '963.  It  has  an  odor  resembling  that 
of  vinegar  and  strong  butter,  and  an  acid  pungent  taste.  It 
is  monobasic,  and  its  salts  are  all  soluble  in  water.  The 
butyrate  of  lime  (CgHyCaC},)  dissolves  readily  in  cold  water, 
but  its  solubility  diminishes  as  its  temperature  is  elevated  :  at 
the  boiling-point  almost  the  whole  of  the  salt  separates  in 
transparent  prisms,  which  redissolve  on  cooling. 

Butyric  Ether ',  C12H12O4.  —  This  is  formed  with  great 
facility  by  distilling  a  mixture  of  butyric  acid  and  alcohol 
with  sulphuric  acid.  It  is  a  colorless  liquid,  slightly  soluble 
in  alcohol,  and  has  an  agreeable  odor  like  pineapples.  It  is 
employed  by  distillers  to  flavor  spirits.  When  a  mixture  of 
butyric  acid  and  glycerine  is  heated  with  sulphuric  acid,  an 


408  ORGANIC    CHEMISTRY. 

oily  liquid  separates  which  appears  to  be  butyrine,  and  yields 
butyric  acid  and  glycerine  by  action  of  alkalies.  It  is  the 
only  glyceride  that  has  been  formed  artificially. 

When  butyrate  of  lime  is  distilled  it  affords  butyrone,  cor- 
responding to  acetone  (733),  and  a  light  colorless  fluid  called 
butyral.  This  has  the  formula  C8H9O2,  and  sustains  the 
same  relation  to  butyric  acid  that  aldehyde  does  to  the  acetic  ; 
when  exposed  to  the  air  it  absorbs  two  equivalents  of  oxygen, 
and  forms  butyric  acid. 

795.  The  oil  of  the  porj>oise  contains  a  peculiar  glyceride 
called  phocenine ;  by  the  action  of  alkalies   it  affords  gly- 
cerine and  valerianic  acid  (745),  which  has  been  described 
under  the  name  of  phoccnic  acid. 

The  saponification  of  butter  affords,  in  addition  to  the 
butyric,  the  volatile  acids  called  caproic,  caprylic,  and  capric. 
They  arc  separated  from  each  other  and  from  butyric  acid 
by  the  different  solubility  of  their  barytic  salts.  The  caproic 
acid  is  C12H,2O4.  It  is  an  oily  liquid,  slightly  soluble  in  water, 
and  has  an  odor  which  resembles  at  the  same  time  that  of 
vinegar  and  of  sweat.  The  caprylic  (CI6HI6O4)  and  the 
capric  (C^H^O.,)  arc  volatile  odorous  acids  closely  resembling 
the  caproic. 

The  action  of  nitric  acid  upon  castor  oil  and  some  other 
fats,  yields  a  volatile  oily  acid  of  a  fragrant  odor  called  the 
t'TKuitkyJic :  it  is  C14H14O4.  The  distilled  water  of  the  rose 
geranium  (Pelargonium  roscum)  contains  another  oily  acid 
allied  to  the  last ;  it  is  called  pdargonic  acid,  and  is  C18H18O4. 

796.  The  preceding  acids  are  all  volatile,  odorous,  more 
or  less  soluble  in  water,  and  although  their  boiling-points  are 
often  elevated,  may  be  distilled  over  with  its  vapor.     Their 
baryta  and  lime  salts  are  soluble  in  water.     The  remaining 
acids  in  the  series   are  solid,  crystalline,  inodorous,  and  in- 
soluble in  water;  their  salts  with  a  base  of  barium  or  calcium 
arc  insoluble,  while  the  potash  and  soda  salts  are  very  soluble 
in  water,  and  are  proper  soaps. 

797.  The  berries  of  the  laurel,  called  Lavrus  nobilis,  con- 
tain a  white  crystalline  glyceride  called  laurine,  which,  when 
sappnified,  affords  the  lavric  acid,  C24H2,O4.     It  is  white  and 
crystalline,  and  fuses  at  88°  :  alcohol  dissolves  it  readily,  and 
the  solution  has  a  strongly  acid  reaction. 

The  oil  of  the  cocoanut  yields,  by  saponification,  cocinic 
^H^O.!  •   it  is  very  fusible  and   resembles   the  last. 
The  nutmeg  contains  a  peculiar  fat  or  glyceride  called  my- 


FATS  AND  THE  SUBSTANCES  DERIVED  THEREFROM.        409 

ristine,  which  yields,  by  the  usual  process,  myristic  acid, 
CasHagQ,.     It  resembles  the  preceding,  and  fuses  at  120°. 

The  palm  oil,  which  is  the  product  of  the  nuts  of  the 
Elais  guinensis,  is  a  mixture  of  a  fluid  fat,  oleine,  with 
a  solid  crystalline  substance  called  palmitine.  This  is  the 
glyceride  of  ethalic  acid,  which  has  been  described  under  the 
name  of  palmitic  acid. 

798.  The  solid  fat  of  animals  is  composed  of  two  solid 
glycerides,  margarine   and   stearine,  with    a   liquid   called 
oleine.*     The  oil  of  olives  and  butter  contains  a  portion  of 
margarine.     It  is  best  obtained  from  animal  tallow  by  dis- 
solving it  in  several  times  its  volume  of  hot  ether.    The  stea- 
rine  crystallizes  out  on  cooling,  and  after  expelling  the  ether 
by  evaporation,  the  margarine  is  obtained  mixed  with  oleine, 
which  may  be  removed  by  pressure  between  folds  of  blotting- 
paper.     Pure  margarine  fuses  at  116°,  and  is  very  soluble  in 
ether ;  by  the  action  of  alkalies  it  yields  glycerine  and  mar- 
garic  acid.     This  acid  is  white,  and  crystallizes   in  pearly 
plates;  it  fuses  at  140°.     Its  composition  is  C^H^C^. 

799.  Stearine  is  obtained   as    a  white   crystalline   mass, 
fusing  at  130°.     It  is  almost  insoluble  in  alcohol  and  cold 
ether.     By  saponification  it  yields  the  stearic  acid ;  this  is 
very  soluble  in  ether  and  alcohol,  and  melts  at  167°.     Its 
formula  is  CggELjgO,!.     The  stearic  ether  is  obtained  by  pass- 
ing hydrochloric  acid  gas  through  a   hot  solution  of  stearic 
acid  in  alcohol ;  it  is   a  white  crystalline  substance,  soluble 
in  alcohol,  but  insoluble  in  water ;  it  fuses  at  88°,  and  by  a 
higher  heat,  is  completely  decomposed.     It  is  the  homologue 
of  acetic  and  butyric  ethers,  and  like  them  is  decomposed  by 
an  alcoholic  solution  of  potash,  taking  up  the  elements  of  two 
equivalents  of  water,  and   regenerating  alcohol  and  stearic 
acid.     The  ethers  of  the  other  fatty  acids  may  be  formed  by 
a  process  similar  to  that  just  described,  and  are  much  more 
fusible  than  the  acids  themselves. 

800.  Bees-wax  may  be  regarded  as  the  aldehyde  of  stearic 
acid  ;  its   formula    is  CggHagOa,  and  it    is   consequently  the 
homologue  of  spermaceti  and  butyral.     When  heated  with 
hydrate  of  potash,  hydrogen  gas  is  evolved,  and  stearic  acid 
formed.     It  is  soluble  in  a  solution  of  potash,  and  forms  a 


*  Stearine.,  from  the  Greek  stear,  tallow,  and  oleine,  from  elaion, 
oil.  Margarine  is  named  from  margarites,  a  pearl,  in  allusion  to 
the  pearly  lustre  of  its  acid. 

35 


410  ORGANIC    CHEMISTRY. 

kind  of  soap  ;  when  boiled  with  a  very  concentrated  potash 
ley,  it  yields  stearic  acid  and  a  volatile  crystalline  substance, 
which  appears  to  correspond  to  the  ethol  of  spermaceti,  and 
to  be  the  alcohol  of  stearic  acid. 

It  has  been  regarded  as  a  vegetable  production,  and  col- 
lected by  bees  from  plants;  but  recent  experiments  have  satis- 
factorily shown  that  bees  produce  wax  when  fed  upon  pure 
sugar  or  honey ;  it  must,  therefore,  be  a  secretion  of  the  insect. 

The  berries  of  the  Anamirta  coculvs  contain  a  peculiar 
glyceride,  which  by  the  action  of  alkalies  yields  the  ana- 
mirtic  acid.  It  closely  resembles  the  preceding  acids,  and 
its  composition  is  C^H^O.,. 

801.  The  fatty  acids  already  described,  are  homologues 
of  formic  and  acetic  acid  ;  they  are  monobasic,  contain  four 
equivalents  of  oxygen,  with  carbon  and  hydrogen  in  equal 
equivalents.  This  will  be  seen  by  arranging  them  in  suc- 
cession. 


1.  Formic,  C2  H2  O4  11. 

2.  Acetic,  C4  H4  O4  12.  Laurie, 

3.  Metacetonic,  Ce  He  O4  13.  Cocinic, 

4.  Butyric,  C*  H8  O4  14.  Myristic, 

5.  Valerianic,  Ci0Hi004  15. 

6.  Caproic,  C12Hi2O4  16.  Ethalic,            C32H32O4 

7.  Enanthylic,  CUH)4O4  17.  Margaric,         C^H^A 

8.  Caprylic,  Ci6Hi6O4  18.  Anamirtic, 

9.  Pelargonic,  CISHj8O4  19.  Stearic, 
10.  Capric, 


The  first,  second,  fifth,  and  sixteenth  of  these  acids  are  de 
rived  from  alcohols  already  known,  and  the  bodies  corres- 
ponding to  aldehyde  in  the  fourth  and  nineteenth,  have  also 
been  discovered ;  we  may  regard  all  of  them  as  the  acids  of 
a  series  of  alcohols  as  yet  unknown.  In  this  group  we  observe 
a  regular  transition  from  the  acetic  and  formic  acids,  through 
the  butyric,  valerianic,  and  other  oily  sparingly  soluble  acids, 
to  the  completely  insoluble  ethalic  and  stearic.  The  eleventh 
and  fifteenth  of  the  series  are  as  yet  unknown,  but  it  is 
highly  probable  that  they  may  yet  be  discovered,  as  well  as 
others  higher  in  the  series.  Three  or  four  of  those  in  the  list 
have  been  described  within  as  many  years. 

The  first  two  acids  in  the  group  which  volatilizes  without 
decomposition,  exhibit  a  progressive  increase  of  about  36°  F. 
in  their  boiling-points;  thus,  the  formic  acid  boils  at  212°, 
=  248°,andthemetacetonic,at248°-H 


FATS  AND  THE  SUBSTANCES  DERIVED  THEREFROM.        411 

802.  Oleic  Acid. — The  fluid  portion  of  butter  and  animal 
fats  consists  principally  of  oleine ;  and  the  vegetable  and  animal 
oils  are  composed  of  oleine  and  a  little  margarine,  or  other 
glycerides.     It  is  obtained  by  exposing  olive  oil  to  cold,  and 
separating  the  margarine  which  crystallizes  out ;  it  is  lighter 
than  water,  tasteless  and  inodorous.     By  the  action  of  alkalies 
it  yields  glycerine  and  oleic  acid.     This  resembles   oleine 
itself,  and  has  neither  taste  nor  smell  ;    it  rapidly  absorbs 
oxygen    from  the   air,  and   is   altered.     Its   composition  is 
CgeH^O^  and  it  is  monobasic,  forming,  like  the  other  fatty 
acids,  soluble  salts  with  the  alkalies. 

When  nitrous  acid  vapor  is  passed  through  oleic  acid,  it 
almost  immediately  solidifies  into  a  crystalline  mass  of 
elaidic  acid,  which  is  purified  by  crystallization  from 
alcohol.  It  forms  superb  crystals  of  a  brilliant  whiteness, 
fusing  at  112°.  Its  composition  is  precisely  similar  to  oleic 
acid,  of  which  it  is  a  metameric  modification.  When  oleic 
or  elaidic  acid  is  heated  with  hydrate  of  potash,  hydrogen 
gas  is  evolved,  and  ethalate  and  acetate  of  potash  are  formed. 
If  oleic  acid  is  boiled  for  a  few  minutes  with  strong  nitric 
acid,  it  is  converted  into  margaric  acid,  which  congeals  on 
cooling :  the  reaction  consists  in  the  separation  of  two 
equivalents  of  carbon  as  carbonic  acid  gas. 

Stearic  acid  affords  the  margaric  by  a  similar  process. 
The  prolonged  action  of  nitric  acid  gives  rise  to  the  volatile 
acids  of  the  preceding  series.  M.  Redtenbacher  has  recently 
observed  in  the  volatile  products  resulting  from  the  action 
of  nitric  upon  the  oleic  acid,  all  those  from  the  acetic  to 
the  capric  inclusive.  The  other  fatty  acids  and  wax  yield 
the  same  products. 

803.  The  residue  of  this  process   contains   four  soluble, 
crystallizable,  bibasic  acids,   the  succinic,  CgH^Og,  adipic, 
C,2H10Og,  pimelic,  Ci4H12O8,  and  suberic,  C16H14O8.     The  suc- 
cinic  acid  was  originally -obtained  by  distilling  amber,  a  fossil 
resin,  which  occurs  in  recent  geological  formations.    Succinic 
acid  is  soluble  in  water  and  alcohol ;  when  heated  it  fuses,  and 
is  decomposed  into  water  and  a  neutral  crystalline  substance 
called   succinide,  C8H4O6,  which  when  boiled  with  water  is 
gradually  reconverted  into  succinic  acid.     The  other  acids 
are  of  but  little  importance ;  the  suberic  is  a  product  of  the 
action  of  nitric  acid  upon  cork.     When  oleine  or  oleic  acid 
is  distilled,  sebasic  acid   is  obtained  ;    it   is    crystallizable, 
volatile,  and  soluble  in  water,  and  has  the  formula 


412  ORGANIC    CHEMISTRY. 

It  is  bibasic  and  homologous  with  the  four  preceding  acids, 
in  all  of  which  the  number  of  equivalents  of  hydrogen  is  less 
by  two  than  the  carbon,  and  the  oxygen  equal  to  eight 
equivalents.  When  these  acids  are  fused  with  hydrate  of 
potash,  hydrogen  gas  is  evolved,  and  salts  of  the  volatile 
acids  of  the  preceding  groups  are  formed.  The  pimelic 
yields  by  this  process  valerianic  acid ;  carbonic  acid  is 
formed  at  the  same  time. 

804.  Soaps. — The  compounds  of  these  acids   are   very 
important,   and   constitute   the    bodies    generally   known    as 
soaps.      These    are    mixtures    of    oleate,    rnargarate,   and 
stearatc  of  potash  or  soda,  being  formed  from   the  saponiii- 
cation  of  mixed  fats  by  these  alkalies.     The  soft  soaps  con- 
tain potash,  and  the  hard  ones  soda.     All   these  compounds 
are  readily  decomposed   by  acids,  which  combine  with   the 
alkali  and   liberate  the  fatty  acid.     When  we  mix  a  solution 
of  soap  with  the  soluble  salt  of  any  other  base,  we  obtain  a 
precipitate  which  is  an  insoluble  combination  of  the  fatty  acid 
with  the  base.     Hence  the  power  of  salts  of  lime  or  magnesia 
to  render  water  hard.     The  compounds  of  these  acids  with 
the  oxyd  of  lead,  constitute  the  lead  plaster,  or  diachylon, 
so  much  used  in   surgery.     A  mixture  of  stearic  and  mar- 
garic  acids,  obtained   by  saponifying  animal  fats  with  lime, 
and  decomposing  the  insoluble  soap   by   hydrochloric  acid, 
has  been  employed  in  the  manufacture  of  candles.     When 
a  solid  fat,  as  lard,  is  kept  for  a  long  time  melted,  especially 
if  a  little  spirit  of  wine  is  mixed  with  it,  the  solid   portions 
separate,  on  cooling,  in  crystalline  grains :  by  subjecting  this 
mass  to  pressure,  the  fluid  part  is  separated,  and  the  mixture 
of  margarine  and  stearine  thus  obtained  is  used  for  the  manu- 
facture of  candles,  while  the  fluid   oleine  constitutes  what  is 
called  lard  oil.  •  Both  of  these  products  are  now  extensively 
manufactured  in  this  country. 

VEGETABLE    ACIDS. 

805.  Besides    those   vegetable   acids    already   described, 
there  are  a  number  of  others,  most  of  which  exist  in  saline 
combination  in  different  plants.     They  are  generally  solid, 
crystallizable,    soluble   in    water,  and   not   volatile    without 
decomposition.     A  few  of  the  more  important  of  them  will  bo 
noticed. 

806.  Oxalic  Acid,  C4H2OS, — The  salts  of  this  acid  exist 


VEGETABLE    ACIDS.  413 

in  many  vegetables :  the  agreeably  sour  taste  of  wood  sorrel, 
Oxalis  acetoselldy  and  other  plants  of  the  same  genus,  is  due 
to  the  acid  oxalate  of  potash  which  they  contain.  Oxalic 
acid  is  a  product  of  the  action  of  nitric  acid  upon  sugar, 
starch,  lignine,  and  many  other  organic  substances.  To 
prepare  it,  one  part  of  starch  is  heated  with  eight  parts  of 
nitric  acid,  specific  gravity  1*25.  A  violent  action  ensues, 
and  much  nitrous  acid  is  evolved  ;  when  this  ceases,  the 
solution  is  concentrated  by  evaporation,  and  on  cooling  yields 
a  large  quantity  of  crystals  of 'oxalic  acid,  which  are  purified 
by  washing  in  water,  and  recrystallization. 

Oxalic  acid  is  colorless,  very  soluble  in  water,  has  a 
powerfully  acid  taste,  and  is  very  poisonous.  It  crystallizes 
with  four  equivalents  of  water,  in  forms  belonging  to  the 
monoclinite  system :  by  a  gentle  heat  the  water  is  expelled, 
and  the  dry  acid,  C4H2O8,  remains ;  this,  by  a  careful  appli- 
cation of  heat,  may  be  in  part  sublimed  unchanged,  but  at  a 
high  temperature  it  is  decomposed  into  formic  acid,  water, 
and  carbonic  oxyd  and  carbonic  acid  gases.  When  oxalic 
acid  or  an  oxalate  is  heated  with  strong  sulphuric  acid,  it  is 
decomposed,  and  a  mixture  of  equal  volumes  of  carbonic 
acid  and  carbonic  oxyd  gases  is  evolved,  C4H2O8=2CO2  + 
2CO  +  2HO,  (347.) 

807.  Oxalic  acid  is  bibasic,  and  forms  neutral  salts  in 
which  two  equivalents  of  its  hydrogen  are  replaced  by  a 
metal,  and  acid  salts  with  but  one  equivalent  of  fixed  base. 
The  neutral  oxalate  of  potash  (C4K2O8)  is  a  very  soluble 
salt.  The  acid  oxalate,  commonly  called  binoxalate  (C4HKO8) 
is  less  soluble,  and  has  an  agreeable  acid  taste.  It  exists,  as 
before  stated,  in  the  juice  of  the  Oxalis  'icetosella,  and  is 
hence  often  distinguished  as  salt  of  sorrel ;  it  is  used  to  remove 
iron  stains  from  linen,  which  it  does  by  forming  a  soluble 
salt  with  the  iron.  When  this  oxalate  is  dissolved  in  hydro- 
chloric acid,  a  salt  separates  on  cooling  which  is  commonly 
called  a  quadroxalate.  Its  composition  is  such  that  it  may 
be  regarded  as  a  compound  of  equal  equivalents  of  oxalic 
acid  and  the  acid  oxalate.  The  neutral  oxalate  of  ammonia 
(C4H2O82NH3)  crystallizes  in  fine  prisms,  and  is  much  used 
in  analytical  chemistry.  When  exposed  to  heat,  it  is  decom- 
posed, and  yields,  among  other  products,  water  and  oxamide. 
This  substance  has  been  already  described  as  the  amide  of 
oxalic  acid,  (698.)  The  acid  oxalate  yields  in  the  same 
manner  the  acid  amide,  oxamic  acid,  which  contains 
35* 


414  ORGANIC    CHEMISTRY. 

C4H2O8,NH3-2HO=C4H3NO6.  When  a  solution  of  oxamic 
acid  is  boiled,  it  reassumes  the  elements  of  water  and  forms 
acid  oxalate  of  ammonia. 

808.  The  Oxalate  of  Lime  (C4CaO8-f  4aq)  is  a  very  in- 
soluble salt,  and  occupies  an  important  part  in  the  vegetable 

economy,  being  secreted  by  a  large  number  of 
plants,  in  the  cells  of  which  the  microscope  re- 
veals to  us  a  great  number  of  beautiful  crystals 
of  this  substance ;  this  appearance  is  repre- 
sented in  the  annexed  figure  of  a  vessel  from 
the  bark  of  Torreya  taxifolia.  In  many  of 
the  lichens,  the  oxalate  of  lime  appears  to  re- 
place the  woody  fibre,  and  to  be  somewhat 
allied  in  its  functions  to  the  carbonates  and 

phosphates  of  lime  in  the  animal  kingdom.    The  oxalates  of 

the  metals  are  generally  insoluble. 

809.  Oxalic  acid   combines  with  two  equivalents  of  the 
alcohols  to  form  neutral  ethers  (703) ;  they  are  obtained  by 
distilling  the  alcohol  and  oxalic  acid  with  a  portion  of  sul- 
phuric acid.     The  oxalic  methylic  ether  crystallizes  finely  ; 
those  of  spirit-of-winc  and  amylol  are  liquids.     The  oxalo- 
rinic  is  a  coupled  acid,  which  corresponds  to  the  sulphovinic, 
(704.)    AVhen  oxalic  ether  is  mixed  with  excess  of  ammonia, 
alcohol  separates,  and  oxamide  is  formed ;  but  if  ammonia 
is  cautiously  added,  only  half  of  the  alcohol  is  eliminated,  and 
a  beautiful  crystalline  compound   called  oxamethane  is  ob- 
tained;  it  is  an  ether-amide,  like  sulphamethylane,  (736.) 

810.  Tartaric  Acid,  C8II6O,2. — This  acid  exists  in  the 
juices  of  many  fruits,  particularly  that  of  the  grape,  as  an 
acid  tartrate  of  potash.     As  this  salt  is  almost  insoluble  in 
dilute  alcohol,   it   is  deposited,   during  the   fermentation,   in 
crystalline  crusts  known  as  crude  tartar,  or  argol.     It  is 
decomposed   by  chalk   to   form   a   tartrate  of  lime ;   this   is 
mixed  with  an  equivalent  of  sulphuric  acid,  which  forms  a 
sulphate,  and  liberates  the  tartaric  acid.    From  a  concentrated 
solution  it  crystallizes  in  fine  rhombic  prisms,  very  soluble  in 
water  and  alcohol,  and  having  a  pleasant  acid  taste.    Tartaric 
acid  is  bibasic,  and  often  forms  salts  with  two  bases. 

811.  The  Acid  Tartrate  of  Potash,  C8H5KOI2,  is  obtained 
by  purifying  the  crude  tartar  of  wine,  and  generally  appears 
as  a  white  crystalline  powder,  known  as  cream  of  tartar. 
It  is  very  little  soluble  in  cold  water,  and  has  a  slightly  acid 
taste;  it  is  extensively  used  in  dyeing  and  in  medicine.     Tho 


VEGETABLE    ACIDS.  415 

neutral  tartrate,  C8H<KjjOH,  is  very  soluble.  The  tartrate 
of  potash  and  soda  is  obtained  by  neutralizing  cream  of 
tartar  by  carbonate  of  soda,  and  forms  very  large  trans- 
parent prismatic  crystals :  it  is  commonly  known  by  the 
name  of  Rochelle  salt.  When  a  mixture  of  water,  cream 
of  tartar,  and  oxyd  of  antimony  is  boiled  together,  solution 
takes  place,  and  on  cooling  transparent  crystals  are  deposited, 
which  are  employed  in  medicine  under  the  name  of  tartar 
emetic.  As  oxyd  of  antimony  is  not  a  protoxyd,  it  obviously 
cannot  replace  the  hydrogen  equivalent  for  equivalent,  but 
one  equivalent  of  its  oxygen  combines  with  one  of  hydrogen 
from  the  acid,  and  the  residues  unite,  C8H5K— OI2  +  Sb2O3— 
C8  (H4Sb2O2K)  O12  -f-  HO.  The  salt  contains,  besides,  ten 
equivalents  of  water  of  crystallization  ;  these  are  expelled  by 
a  gentle  heat,  but  if  the  temperature  is  carried  to  428°  two 
more  equivalents  of  water  are  given  off,  and  a  salt  remains 
which  is  C8(H2Sb2K)O12.  Arsenious  acid  forms  similar 
compounds.  Tartaric  acid  dissolves  peroxyd  of  iron,  and 
forms  a  very  soluble  salt :  in  this  as  well  as  in  the  preceding 
compounds,  the  metal  is  so  combined  as  not  to  be  pre- 
cipitated by  potash  or  ammonia. 

Tartaric  acid  yields  with  alcohol  an  ether  and  a  coupled 
acid,  the  tartromnic.  When  tartaric  acid  is  heated  it  loses 
the  elements  of  water,  and  forms  several  new  acids  which 
are  of  no  particular  interest. 

812.  Racemic,  or  Parataric  Acid,  C8H6O,2. — This  acid 
is  isomeric  with  the  preceding,  and  is   often  associated  with 
it   in    the  juice  of  the   grape.     It   is    bi basic,   and  closely 
resembles  the  tartaric  acid  in  its  properties  and  the  results  of 
its  decomposition   by  heat,  but  is  distinguished  from  it  by 
several   characters ;  it  is  less  soluble,  and  crystallizes  with 
one  equivalent  of  water,  while  the  crystallized  tartaric  acid 
is  anhydrous ;  the  double  racemate  of  potash  and  soda  is 
very  difficultly  crystallizable,  while  the  double  tartrate  crys- 
tallizes readily  ;  the  racemic  acid  precipitates  solutions  of  the 
salts  of  lime,  which  are  not  affected  by  the  tartaric ;  finally, 
the  salts  of  the  racemovinic  acid  are  different   from  those  of 
the  tartrovinic. 

813.  Malic  Acid,  C8H6O10. — This  acid  exists  in  the  juices 
of  most  sour  fruits,  particularly  in  the  apple.*     The  stems 
of  the  garden  rhubarb  contain  a  large  quantity  of  it.     It  is 

*  Whence  the  name  of  the  acid,  from  the  Latin  mahtm. 


416  ORGANIC    CHEMISTRY. 

very  soluble  in  water  and  alcohol,  and  crystallizes  with  diffi- 
culty ;  its  solution  has  a  pleasant  sour  taste.  This  acid  is 
bibasic.  The  malates  of  the  alkaline  metals  are  very  soluble. 
The  acid  rnalate  of  ammonia  (C8H6O10,NH3)  forms  large 
transparent  crystals ;  the  neutral  malate  of  lead  (C8H4Pb2O10) 
is  obtained  as  a  white  precipitate,  which,  if  left  for  some  time 
in  a  liquid  containing  free  acid,  changes  into  delicate  crystals. 

814.  When  malic  acid  is  heated  to  350°,  it  is  decomposed 
into  water  and  two  new  acids,  the  maleic  andfumaric,  which 
are  isomeric,  and  derived  from  the  malic  by  the  abstraction 
of  the   elements   of  water,  C8H6O10-2HO=C8H4O8.     The 
maleic  acid  is  obtained  dissolved  in  the  water,  which  distils 
over;   it  is  crystallizable,  and  very  soluble.     This  acid  is 
identical    with    the   equisetic   acid   obtained    from   different 
species  of  the  Equisetum.     When  heated  for  some  time  to 
320°,  it  is  converted  into  fumaric  acid  ;  this  remains  in  the 
retort  after  the  decomposition  of  maleic  acid,  and  is  also  found 
in  the  fumitory,  (Fumaria  afficinalis,)  and  in  Iceland  moss. 
It  has  the  same  composition  as  the  maleic,  and  like  it  is  bibasic, 
but  is  distinguished  by  being  very  sparingly  soluble  in  cold 
water. 

815.  Citric   Acid,   C,2H8Oi4.  —  This  acid   exists   in   the 
juices  of  many  fruits,  often  associated  with   the  tartaric  and 
malic,  and  is  the  cause  of  the  acid  taste  of  the  lemon.     It  is 
obtained  by  saturating   lemon-juice  with  chalk,  by  which  an 
insoluble  citrate  of  lime  is  formed  ;  this  is  decomposed  with 
an  equivalent  of  sulphuric  acid,  which  forms  a  sulphate  of 
lime,  and  the  citric  acid  is  obtained  by  evaporation  and  crys- 
tallization.    It  forms  large  crystals  pertaining  to  the  trime- 
tric  system  ;  it  is  very  soluble  in  water,  and  has  a  strong  but 
agreeable  acid  taste.     The  citric  acid  is  tribasic,  and  forms 
with  potash  three  salts,  which  are  C12H7KOi4,  Ci2H6K2O14,  and 
C,2H5K3Oi4 ;  the  first  two  are  acids.     The  citrates  are  unim- 
portant. 

816.  When  the  citric  acid  is  exposed  to  heat  in  a  retort, 
it  evolves  water,  and  it   is  converted  into  aconitic  acid  ;  its 
composition   is   C,2H8O,4 — 2HO  =  C12H6012.      This  acid   is 
found  combined  with   lime   in  the  Aconitum  napellus ;  it  is 
tribasic,  and  very  soluble  in  water.     If,  in  the  decomposition 
of  citric  acid,  we  carry  the  heat  further,  the  aconitic  acid  is 
decomposed  into  carbonic   acid    gas   and    citraconic  acid, 
C,2H6O]2=2CO2+C10H6O8.     This  last  distils  over  as  an  oily 
iluid,  which  forms  a  crystalline  mass  on  cooling.     This  acid 


VEGETABLE    ACIDS.  417 

is  bibasic,  and  readily  soluble  in  water  ;  when  carefully 
heated  it  sublimes  unchanged,  but  by  a  greater  heat  it  is  de- 
composed into  water  and  a  neutral  liquid,  called  citraconide, 
C,0H4O6.  This  slowly  dissolves  in  water,  and  is  converted 
into  an  acid,  which  is  isomeric  with  the  citraconic,  though 
differing  in  its  properties. 

817.  Tannic  Acid  ;  Tannin,  CXH]GOU. — The  bark  and 
leaves  of  many  plants  contain  a  peculiar  substance,  which  is 
characterized  by  possessing  an  astringent  taste,  and  by  pre- 
cipitating gelatine  from  its  solutions.  This  principle  is  abun- 
dant in  the  bark  of  many  oaks,  and  in  nut-galls,  which  are 
excrescences  resulting  from  the  puncture  of  an  insect  upon  a 
species  of  oak.  The  infusion  of  oak-bark  or  nut-galls,  pre- 
cipitates solutions  of  persalts  of  iron,  of  a  bluish-black 
color.  The  vegetable  extracts,  kino  and  catechu,  resemble 
the  tannin  of  the  oak,  but  differ  in  the  color  of  their  precipi- 
tates with  solution  of  iron,  and  hence  some  chemists 
have  considered  them  as  distinct.  It  is,  however, 
more  probable  that  the  tannin  which  they  contain  is 
identical  with  that  of  the  oak,  but  modified  in  its  reac- 
tions by  the  presence  of  other  vegetable  acids.  Tan- 
nin is  best  obtained  from  gall-nuts,  which  yield 
thirty  or  forty  per  cent,  by  the  following  process. 
The  gall-nuts  in  coarse  powder  are  placed  in  the  upper 
vessel  represented  in  the  figure,  the  mouth  of  which  is 
previously  stopped  by  a  piece  of  linen.  A  quantity 
of  washed  ether  (715)  is  then  poured  over  them, 
which  slowly  filters  through,  and  collects  in  the  lower 
vessel,  where  it  separates  into  two  layers.  The 
lower  is  an  aqueous  solution  of  pure  tannic  acid, 
while  the  lighter  fluid  is  ether,  holding  in  solution  the 
coloring  matter  of  the  gall-nut  and  other  impurities. 
The  ether  used  in  this  process  contains  about  one- 
twelfth  part  of  water,  which  dissolves  the  tannic  acid 
to  the  exclusion  of  all  other  substances.  The  solution  of 
tannin  is  separated  by  means  of  a  funnel,  washed  with  a  little 
ether,  and  finally  evaporated  in  shallow  vessels  by  a  gentle 
heat.  It  forms  a  brilliant  porous  mass  which  has  generally 
a  light  yellow  tint ;  it  is  very  soluble  in  water,  and  the  solu- 
tion has  a  purely  astringent  taste.  The  tannic  acid  is  a  feeble 
acid  ;  it  dissolves  the  alkaline  carbonates  with  effervescence. 
Its  solution  throws  down  insoluble  compounds  from  solutions 
of  nearly  all  the  metallic  salts,  giving  precipitates  which  are 


418  ORGANIC    CHEMISTRY. 

often  very  characteristic  ;  with  pcrsalts  of  iron  it  yields  a  pur- 
plish-black, which  is  the  basis  of  ordinary  writing-ink  and 
black  dyes.  With  baryta  it  forms  salts  which  are  CxHl5B'dO^ 
and  C36H|4Ba2O24 ;  it  is  therefore  bibasic. 

818.  This  substance  does  not  form  an  ether  with  alcohol 
like  the  other  acids,  and  from  many  of  its  characters  it  seems 
to  be  more  allied  to  sugar  and  gum,  which,  like  it,  have  the 
power  of  neutralizing    bases  without   possessing   the   other 
attributes  of  acids. 

Tannin  is  very  liable  to  decomposition ;  when  a  dilute  so- 
lution is  exposed  to  the  air,  it  gradually  absorbs  oxygen -and 
evolves  carbonic  acid  gas,  and  is  converted  into  gallic  acid. 

819.  Gallic  Acid,  C14H6O10. — This   is   a  product  of  the 
decomposition  of  tannin  by  exposure  to  the  air,  by  the  action 
of  alkalies   and  acids,  and  by  various  ferments.     It  is  best 
obtained  by  exposing  a  mixture  of  pulverized  gall-nuts  and 
water  to  the  air,  for  two  or  three  months  in  summer.     A 
peculiar  fermentation  ensues,  and  the  tannic  is  converted  into 
gallic  acid.    It  is  readily  dissolved  out  by  boiling  water,  which 
deposits  it  on  cooling  in  small  silky  crystals,  which  have  an 
acid  and  astringent  taste.     It  does  not  precipitate  gelatine, 
and  the  black  porgallate  of  iron  loses  its  color  when  heated. 
This   acid  is  bibasic,  but  its  salts  have  been  little  studied. 
Gallic  acid  exists  in  large  quantities  in  the  fruit  of  the  mango  ; 
its  formation  from  tannin  is  not  well  understood. 

Gallic  acid  dissolves  in  hot  sulphuric  acid,  and  on  cooling 
the  solution  deposits  a  reddish  brown  crystalline  powder  called 
galleide  ;  it  is  gallic  acid  minus  two  equivalents  of  water. 

There  arc  in  addition  to  these  many  other  vegetable  acids, 
which  are  described  in  the  larger  works,  but  their  characters 
have  not  generally  been  much  studied. 

VOLATILE    OR    ESSENTIAL    OILS. 

820.  These  terms  are  applied  to  a  large  class  of  products 
which  are  obtained  by  distilling  plants  with  water,  and  they 
generally  possess  in  a  high  degree  the  peculiar  odor  of  the 
plants  from  which  they  are  derived.    They  are  very  different 
in  chemical  characters ;  some  of  those  which  contain  oxygen, 
as  the  oils  of  meadow-sweet,  bitter  almonds,  cumin,  and  cin- 
namon, have  been  already  described ;  and  many  others  of 
less  importance  are  analogous  in  their  composition. 

821.  Many  of  them  consist  of  carbon  and  hydrogen  only ; 


VOLATILE   OR   ESSENTIAL    OILS.  4<19 

and  a  large  class  which  contain  these  elements  in  the  ratio 
of  eight  to  five,  and  combine  directly  with  hydrochloric  acid, 
are  distinguished  by  the  general  name  of  camphene  :  of  these 
the  oil  of  turpentine  is  the  most  important ;  it  is  obtained  by 
distillation  from  the  crude  turpentine,  which  exudes  from 
many  species  of  Pines,  and  is  a  colorless,  aromatic  liquid  of 
a  peculiar  taste,  having  a  specific  gravity  of  -865,  and  boiling 
at  312°.  It  is  of  great  use  in  the  arts  for  the  preparation  of 
varnishes,  and  when  carefully  purified  is  employed  for  pur- 
poses of  illumination  under  the  names  of  camphene  and  pine 
oil.  Its  formula  is  C2oH16.  When  dry  hydrochloric  acid  is 
passed  through  the  cooled  oil,  it  is  rapidly  absorbed,  and  a 
white  crystalline  compound  of  the  two  separates  from  a  liquid 
of  the  same  composition  as  the  solid.  It  contains  the  ele- 
ments of  one  equivalent  of  the  oil  and  one  of  the  acid  ;  the 
acid  is  so  combined  that  it  cannot  be  detected  by  the  salts  of 
silver,  and  we  may  regard  this  compound  as  the  chlorinized 
species  of  a  hydrocarbon,  which  is  Cg)HI8.  It  is  volatile,  and 
has  a  fragrant  odor  like  camphor,  and  for  this  reason  it  was 
formerly  called  artificial  camphor. 

822.  When  moist  oil  of  turpentine  is  exposed  to  cold   it 
often  deposits  crystals,  which  contain  the  elements  of  the  oil 
plus   four   equivalents   of  water  ;    the  same   compound    is 
slowly  deposited   from  a  mixture  of  the  oil  with  nitric  acid 
and  alcohol.     It  forms   colorless  prismatic  crystals,  soluble 
in  hot  water  and  in  alcohol;  its  composition  is  C^^O^-i- 
2aq  ;  the  two  equivalents  of  water  are  expelled  by  heat ;  the 
name  of  terebol  is  given  to  this  substance. 

823.  Among  the  other  oils  included  under  the  name  of 
camphene,  are  those  of  juniper,  pepper,  caraway,  parsley, 
citron,  orange,  lemon,  and   bergamot.      All  of  these  have 
the  same  boiling-point,  and  the  same  density  of  vapor  as  the 
oil  of  turpentine,  and  like  it  combine  with  hydrochloric  acid 
to  form  solid  or  liquid  compounds ;  the  oil  of  citron  combines 
with   two   equivalents  of  the   acid.     Many   of  them   yield 
terebol   by   the   action   of   nitric   acid   and   alcohol.      The 
difference  in  the  odor  of  these  oils  is  quite  unexplained ;  it 
does  not  arise,  as  has  been  supposed,  from  the  presence  of 
an   oxydized   compound,   for   they   may   be   distilled    from 
hydrate  of  potash,  or  from  potassium,  without  any  other 
effect  than  that  of  refining  the  odor.     The  oil  of  roses  is  a 
carburet  of  hydrogen,  probably  C^H^. 

824.  Many  of  the  essential  oils  of  both  classes  deposit 


420  ORGANIC    CHEMISTRY. 

crystalline  compounds  when  cooled  ;  they  are  often  isomeric 
with  the  oxygenized  oils,  and  sometimes  are  analogous  to 
the  terebol  in  their  relations ;  these  bodies  are  designated  as 
stcaroptens  or  camphors,  from  their  resemblance  to  common 
camphor.  This  last  substance  is  a  product  of  the  Laurus 
camphora,  and  is  obtained  by  distilling  the  wood  of  the  tree 
with  water.  It  is  a  light,  volatile,  and  combustible  solid,  of 
a  strong  and  fragrant  odor.  It  is  soluble  in  alcohol,  but 
insoluble  in  water.  Its  formula  is  CKH]6O2.  By  long 
boiling  with  strong  nitric  acid,  it  is  converted  into  camphoric 
acid,  CXHWOS. 

825.  Borneo  Camphor. — This  substance  is  obtained  from 
the  Dnjabalanops  cajnphora  of  Borneo ;  it  is  also  found  in 
the  essential  oil  of  valerian.     It  resembles  the   laurel  cam- 
phor, but  its  odor  is  similar  to  that  of  pepper,  and  it  has  a 
pungent   taste.     It   is  very  much   valued   in   the  East,  and 
rarely  reaches  this  country.     Its  formula  is  CKlilkO2 ;  when 
distilled  with  anhydrous  phosphoric  acid,  it  loses  the  elements 
of  water,  and  yields  a  carbohydrogen,  C^IIig.     This  is  called 
borncem:,  and  occurs  with  the  camphor  in  the  Dryabalanops  ; 
it  is  a  camphenc,  and  in  contact  with  water  gradually  fixes 
the   elements   of    two   equivalents    of  that   substance,    and 
regenerates  the  camphor.     Borncene  exists  in  the  essence  of 
valerian,  and  the  camphor  which  this  last  contains  is  formed 
only  when  the  oil  is  moist. 

When  this  camphor  is  boiled  with  nitric  acid,  it  loses 
two  equivalents  of  hydrogen,  and  is  converted  into  laurel 
camphor. 

826.  Oil   of  Mustard.  —  The   seed    of   black    mustard, 
(Sinapis   nigra,)    when    bruised    with  water   and    distilled, 
affords  a  pungent  oil,  which  contains  sulphur  ;  its  formula  is 
C8H5NS2 ;  with  ammonia  and  other  substances  it  affords  many 
interesting  products.     When  heated  with  potassium  a  decom- 
position ensues  ;  sulphocyanid  of  potassium  is  formed,  and  a 
fluid  distils  over,  which  is  identical  with   the  essential  oil  of 
garlic,  as  obtained  when   this   plant   is  distilled   with  water. 
The  reaction  between  these  bodies  is  not  definitely  known. 
The  essential  oils  of  assafcetida  and  many  of  the  cruciferse, 
as    horse-radish,  radish,  and   cress,  contain   sulphur  and  are 
analogous  to  the  preceding.     The  odorant  secretion  of  the 
Mephitis  putorius,  or  pole-cat,  contains  a  large  amount  of  sul- 
phur, and  is,  perhaps,  of  the  same  class. 

827.  Caoutchouc,  Gum-Elastic. — This  curious  substance 


COLORING    MATTERS.  421 

is  not  a  resin,  but  is  mentioned  here  for  convenience  ;  it  is 
found  in  the  juices  of  many  plants,  but  is  principally  obtained 
from  the  Hevea  quianensis,  and  latropha  elastica.  Its 
ordinary  properties  are  well  known ;  it  is  insoluble  in  water  and 
alcohol,  but  dissolves  in  ether  and  many  volatile  hydrocar- 
bons, of  which  the  pure  camphene  is  the  best ;  when  softened 
by  these  solvents,  it  is  wrought  into  a  great  variety  of  curious 
and  useful  articles.  Small 
tubes  of  gum-elastic  are  very 
useful  in  the  laboratory,  to  join 
glass-tubes,  and  form  flexible 
joints,  (381,  Fig.)  They  are 
easily  made  from  sheet  caout- 
chouc by  cutting  the  folded 
edges  of  the  sheet  with  clean 
scissors  over  a  glass  tube,  as  seen  in  the  figure.  It  is  very 
combustible,  and  burns  with  a  bright  smoky  flame.  Caout- 
chouc is  composed  of  carbon  and  hydrogen  in  equal  equiva- 
lents, but  as  it  is  not  volatile,  and  forms  no  compounds,  its 
equivalent  cannot  be  determined  ;  though,  from  the  action  of 
heat  upon  it,  it  is  probably  very  high.  When  exposed  to  heat, 
it  is  decomposed  and  yields  several  volatile  liquids  which  con- 
tain carbon  and  hydrogen  in  equal  equivalents,  and  are  con- 
sequently homologous  with  olefiant  gas;  among  these  is 
butyrene,  C8H8,  and  two  others,  which  are  C,0H,0  and  C40H40. 
These  mixed  fluids  are  employed  as  a  solvent  for  caoutchouc. 
828.  Gutta  Percha  is  the  product  of  a  large  tree  called 
Percha,  (pronounced  pertcha,)  found  in  the  island  of  Singa- 
pore and  adjacent  parts,  which,  when  felled  and  peeled,  gives 
a  milky  juice,  that  being  exposed  to  the  air  soon  coagulates. 
It  has  lately  been  used  in  the  arts  as  a  substitute  for  caout- 
chouc, which  substance  it  much  resembles  in  chemical  proper- 
ties. Submitted  to  analysis,  it  gave  carbon  87-8,  hydrogen 
12-2  ;  while,  according  to  Farraday,  caoutchouc  gave  carbon 
87'2,  hydrogen  12-8.  Its  action  with  solvents  is  the  same  as 
caoutchouc,  but  it  is  much  less  elastic.  The  specific  gravity 
of  gutta  percha  is  0-9791 ;  that  of  caoutchouc  0*9355. 

COLORING    MATTERS. 

Under  this  head  may  be  conveniently  described  a  number 
of  bodies  of  vegetable  and  animal  origin  which  are  employed 
in  the  various  processes  of  dyeing  and  coloring.     But  few 
36 


422  ORGANIC    CHEMISTRY. 

of  them   have  been  accurately  studied,  and  we  shall  men- 
tion only  some  of  the  more  important. 

829.  The  yellow  coloring  matters  of  plants  are  gener- 
ally non-azotized  substances.     Among  the  most  important,  are 
quercitrine,  the  coloring  principle  of  the  Quercus  tinctoria, 
and  luteoline,  from  the  woad,  Reseda  luteola,  both  of  which 
are  soluble  and  crystalline.     The   yellows  of  turmeric  and 
gamboge  are  of  a  resinous  nature.     Others  employed  in  dye- 
ing are  Morine,  from  the  Morus  tinctoria,  and  annatto. 

830.  The  red  coloring  matters  of  alkanet  arid  carthamus 
are  insoluble  in  water,  but  dissolve  in  alkalies  and  are  pre- 
cipitated  by  acids  ;  they  appear  to  possess   acid  properties. 
The  latter,  carthaminc,  is  the  color  of  the  pink  saucers  so 
much  used  in  dyeing.     The  coloring  principle  of  madder  is 
called  alizarine  ;  it  is  volatile,  and  forms  orange- red  crystals. 
Hematoxyline  is  obtained  from  log-wood  ;  it  is  very  soluble, 
and  forms  yellow  crystals  ;  its  solution  is  reddened  by  acids, 
and  rendered   blue   by  alkalies.     It  gives  a  violet  color  with 
alum,  and  a  black  with  porsalts  of  iron. 

Carmine. — This  substance  is  extracted  from  the  insect 
called  cochineal.  When  pure,  it  is  a  dark  red  crystalline 
powder,  which  contains  nitrogen.  The  pigment  known  as 
carmine,  is  a  compound  of  this  principle  with  alumina. 

831.  The  green  color  of  the   leaves  of  plants  is  due  to  a 
substance  called  chlorophyle  ;  it  somewhat  resembles  wax, 
and  is  soluble  in  alcohol,  but   insoluble   in  water.     The  blue 
color  of  flowers   is  very  perishable,  and  has   not  been  accu- 
rately examined. 

832.  Coloring  matters  derived  from   the    Lichens. — A 
number  of  plants  of  this  class  furnish  beautiful  blue  and  red 
coloring  substances,  which   are  used  in     dyeing,   under  the 
names  of  archil,  cudbear,  and   litmus.     These  are   derived 
from  certain   uncolored  principles  contained   in   the  plants. 
Their  nature  may  be  understood  from  a  description  of  one  or 
two  of  these  bodies. 

833.  Lccanorine  is  obtained   from   a   number  of  lichens ; 
it  is  a  white  crystalline   body,  which  when  boiled  with  water 
evolves  carbonic  acid,  and  is  transformed  into  orcine.     This 
forms  large  colorless  crystals,  which  are  volatile,  have  a  sweet 
taste,  and  are  very  soluble   in  water;  its  formula  is  C16H8O4. 
When  mixed  with  ammonia  and  exposed  to  the  air,  it  absorbs 
oxygen  and  is  converted  into  a   deep   red  matter,  which  is  a 
compound  of  ammonia  with  a  new  substance  named  orceine  ; 
this  is  obtained  by  decomposing  a  solution  of  the  ammoniacal 


INDIGO.  423 

compound  with  acetic  acid,  which  precipitates  it  as  a  reddish 
brown  powder.     Its  formula  is  C16H9NO6. 

834.  Many  other  lichens  contain    substances  which   are 
very  similar  to  lecanorine,  and  like  it,  produce  fine  red  com- 
pounds.    The  bruised  plants  are  mixed  with  water,  lime,  and 
an  ammoniacal  salt,  when  they  undergo  a  kind  of  fermenta- 
tion, and  generate  the  red  substances.     These  colors   are 
rendered  blue  by  alkalies,  but  acids  immediately  restore  the 
color.    As  the  reddening  of  paper  colored  blue  by  an  infusion 
of  litmus  is  often  referred  to  as  a  test  of  acidity,  it  is  well  to 
understand  the  principles  upon  which  this  reaction  depends. 
In  litmus  the  red  of  the  orceine  is  changed  to  blue  by  the 
presence  of  lime.     Any  substance  having  a  stronger  affinity 
for  the  lime  than  the  orceine  has,  will  combine  with  it  and 
restore  the  color.     The  neutral  salts  often   redden   litmus- 
paper  ;  sulphate  of  copper,  for  example,  is  decomposed  by 
the  lime  of  the  litmus,  forming  sulphate  of  lime ;  and  as  the 
oxyd  of  copper  which  is  set  free  does  not  affect  the  orceine, 
the  red  color  is  restored  precisely  as  if  sulphuric  acid  had 
been  employed.     Test-papers  prepared  by  an  alcoholic  infu- 
sion of  purple  dahlias,  are  very  sensitive,  turning  green  by 
the  action  of  alkalies,  remain  blue  in  neutral  solutions,  and 
become  red  in  acids. 

INDIGO. 

835.  This  important  coloring  substance  is  obtained  from  a 
great  number  of  plants,  the  principal  of  which  are  the  Indigo- 
fera  tinctoria  and  7.  anil,  with  some  species  of  the  genera 
Isatus,  Nerium,  and  Polygonum.     The  juices  of  these  con- 
tain a  peculiar  colorless  substance  in  solution,  which,  when 
exposed  to  the  air,  absorbs  oxygen,  and  is  converted  into 
indigo.     In  the  manufacture  of  this  substance  the  plants  are 
steeped  in  water,  and  made  to  undergo  a  kind  of  fermentation ; 
the  clear  liquid  is  then  exposed  to  the  air,  and  frequently 
agitated  to  facilitate  the  absorption  of  oxygen;  by  this  pro- 
cess it  gradually  becomes  blue,  and  deposits  the  insoluble 
indigo. 

836.  Commercial  indigo  is  obtained  in  strongly  cohering 
masses  of  a  deep  blue,  which  assume,  when  rubbed,  a  cop- 
pery metallic  lustre.     That  of  commerce  is  never  pure,  but 
is  mixed  with  various  foreign  matters.     Indigo  is  insoluble  in 
water,  alcohol,  oils,  dilute  alkalies,  and  hydrochloric  acid; 
when  cautiously  heated  it  is  volatilized  in  a  purple  vapor, 


424«  ORGANIC    CHEMISTRY. 

which  condenses  in  delicate  crystals.     The  composition  of 
indigo  is  expressed  by  C,6H5NO2. 

In  contact  with  water  and  deoxydizing  agents,  indigo  is 
converted  into  a  colorless  substance,  which  is  soluble  in 
alkaline  liquids ;  this  is  generally  effected  by  a  mixture  of 
lime  and  sulphate  of  iron;  one  part  of  indigo  in  fine  powder, 
four  parts  of  quick  lime,  and  three  of  protosulphate  of  iron, 
are  digested  with  a  large  quantity  of  water.  The  pro- 
toxyd  of  iron  formed  by  the  action  of  the  lime  reduces  the 
indigo,  which  in  this  form  is  dissolved  by  the  alkaline 
solution,  forming  a  yellow  liquid.  If  this  is  exposed  to  the 
air,  oxygen  is  absorbed,  and  the  indigo  is  separated  in  its 
original  color  and  insolubility.  It  is  by  impregnating  cloth 
with  this  solution,  and  precipitating  the  indigo  in  its  texture 
by  the  action  of  the  air,  that  the  fine  indigo-blue  colors  are 
produced. 

837.  Hydrochloric   acid    added   to   this   yellow    solution 
precipitates   the  dissolved    substance  as  a   gray   crystalline 
powder,  which,  when   moist,  rapidly   becomes   blue   by  ab- 
sorbing oxygen,  and  is  converted   into  indigo.     It  is  called 
indiffogene,  and  has  the  formula  C16H6NO2 ;  by  the  addition 
of  one  equivalent  of  oxygen,  it  is  converted  into  indigo  and 
water,    C16H6NO2  +  O=HO  +  C16H,NOa.      In    its    formation 
an  equivalent  of  water  is  decomposed,  its  oxygen  combining 
with  the  oxyd  of  iron.     When  indigo  is  mixed  with  a  boiling 
alcoholic  solution  of  caustic  soda  or  grape  sugar,  it  is  con- 
verted into  indigogene,  while  formic  acid  is  produced  by  the 
oxydation  of  the  sugar.     This  alcoholic  solution,  exposed  to 
the  air,  deposits  pure  indigo  in  crystals. 

838.  Concentrated  sulphuric  acid  dissolves  indigo,  by  the 
aid  of  a  gentle  heat,  and  forms  two  acids,  (704,)  which  are 
formed   by  the  couplement  of  one  and   two  equivalents  of 
indigo    with   one   of  sulphuric   acid,    the    elements   of  two 
equivalents  of  water  being  eliminated.     They  are  named  the 
sulphindigotic,  and  gulphopurpuric  acids.     These  acids  and 
their  salts  are  intensely  blue.     The  first  named  is  the  most 
important;  when  a  solution  of  sulphindigotic  acid  is  boiled 
with  woolen  cloth,  it  is  completely  decolorized,  the  acid  being 
taken  up  by  the  cloth  :  in  this  way  the  color  called   Saxon 
blue  is  obtained.     It  resists  completely  the  action  of  water, 
but  is  easily  dissolved  out  by  a  solution  of  the  carbonate  of 
ammonia,  which  distinguishes  it  from  the  blue  color  obtained 
with  solutions  of  indigogene. 

839.  When  indigo  in    powder  is  heated  with  dilute  nitric 


INDIGO.  425 

acid,  it  dissolves,  forming  a  yellow  solution,  which  affords 
by  evaporation  orange-red  crystals  of  a  new  compound, 
called  isatine.  It  forms  beautiful  rhombic  prisms,  which  are 
sparingly  soluble  in  cold  water,  but  are  readily  dissolved  by 
hot  water  and  alcohol.  It  is  derived  from  indigo  by  the  addi- 
tion of  two  equivalents  of  oxygen,  and  its  formula  is 
C16H5NO4.  When  mixed  with  a  solution  of  potash,  it  forms 
isatinic  acid,  which  contains  the  elements  of  isatine  plus  one 
equivalent  of  water,  and  is  decomposed  by  a  gentle  heat  into 
these  substances.  With  ammonia,  isatine  yields  a  variety 
of  amides,  which  are  derived  from  one,  two,  or  three  equiva- 
lents of  isatine,  by  the  action  of  one  or  more  of  ammonia. 

When  isatine  or  indigo  is  distilled  with  the  hydrate  of  pot- 
ash, carbonate  of  potash  remains,  while  hydrogen  gas  is 
evolved,  with  a  peculiar  oily  liquid,  called  anilene,  which 
will  be  described  among  the  organic  alkaloids.  Its  formula 
is  C12H7N. 

840.  Indigo  dissolves  in  a  boiling  concentrated  solution  of 
potash,  and  forms  a  yellow  solution,  which  contains  isatinate 
of  potash ;  but  if  the  solution  is  evaporated    and    kept    for 
some  time  in   gentle   fusion,  hydrogen   is   disengaged,  and  a 
new  salt,  the  anthranilate  of  potash,  formed.     The  anthrani- 
lic  acid  has  the  composition  C14H7NO4,  and  is  derived  from 
the  elements  of  indigo  and  water  thus,  C16H5NO2  +  6HO  = 
C,4H7NO4  +  2CO2  +  4H.     Anthranilic  acid    crystallizes  in 
colorless    needles,  and   is  soluble   and  volatile,  but   if  mixed 
with  sand  or  pounded  glass  and  rapidly  distilled,  it  is  com- 
pletely resolved  into  carbonic  acid   and  anilene,  C14H7NO4= 
2CO2  +  C)2H7N. 

841.  The  action  of  chlorine  upon  indigo  or  isatine  yields 
two  compounds   called   chlorisatine   and  bichlorisatine,  in 
which  chlorine  replaces  one  and  two  equivalents  of  hydrogen. 
These  substances  closely  resemble  the  normal  isatine  in  their 
properties ;  they  yield  acids  similar  to  the  isatine,  and  when 
distilled  with  hydrate  of  potash  afford  organic  bases  which 
correspond  to  anilene,  in  which  one  and  two  equivalents  of 
chlorine  replace  hydrogen. 

By  the  action  of  hydrosulphuret  of  ammonia,  isatine  com- 
bines with  one  equivalent  of  hydrogen,  and  is  converted  into 
isatyde,  C16H6NO4 ;  sulphureted  hydrogen  yields  with  isatine 
sulphisatine,  C16H6NO2S2.  A  solution  of  potash  removes  the 
sulphur,  and  produces  a  rose-colored  crystalline  substance, 
incline,  which  is  isomeric  with  indigogene. 

842.  When  indigo  is  boiled  for  some  time  with  dilute  nitric 
36* 


426  ORGANIC    CHEMISTRY. 

acid  it  is  converted  into  ammonia,  carbonic  acid,  and  anilic 
or  nitrosalicylic  acid,  (762.)  The  reaction  which  produces 
salicylic  acid  is  thus  represented,  Clt;H5NO2  +  4HO-fO4= 
2CO2-j-NH3  +  C14— HA.  The  prolonged  action  of  nitric 
acid  converts  anilic  acid  into  carbonic  and  nitrophenisic  acids, 
(763.) 

The  final  product  of  the  action  of  chlorine  upon  isatine  is 
a  volatile  substance,  crystallizing  in  golden  yellow  scales. 
It  is  called  chloranilc,  and  is  C,2C1.,O4.  This  substance  is 
also  produced  by  the  action  of  chlorine  upon  salicylic,  anilic, 
and  nitrophenisic  acids,  and  many  other  bodies ;  it  is  easily 
prepared  by  boiling  them  with  a  dilute  hydrochloric  acid  and 
chlorate  of  potash. 

ORGAMC    BASES,    OK    ALKALOIDS. 

843.  These  names  are  employed  to  designate  a  class  of 
bodies  which,  like  ammonia,  unite  with  acids  and  neutralize 
them,  forming  salts.  This  mode  of  combination  is  quite 
distinct  from  that  of  the  metallic  oxyds  with  the  same  acids  ; 
these  unite  with  the  separation  of  the  elements  of  water, 
while  the  salts  of  the  organic  alkaloids  are  formed  by  direct 
union,  (677.)  The  alkaloids  combine  with  metallic  salts  as 
well  as  with  the  acids  themselves  :  for  example,  theine  and 
strychnine  combine  with  nitric  acid,  (NHO6,)  and  with  nitrate 
of  silver,  (NAgOfi,)  forming  in  both  cases  neutral  crystalline 
compounds;  the  hydrochloratcs  of  the  alkaloids  unite  with 
chlorid  of  platinum  to  form  crystalline  and  sparingly  soluble 
salts  resembling  the  corresponding  compound  of  sal  am- 
moniac and  platinum. 

All  of  the  alkaloids  contain  nitrogen  ;  they  may  be  con- 
veniently divided  into  those  which  are  composed  of  carbon, 
hydrogen,  and  nitrogen  only,  and  those  that  contain  oxygen. 
The  first  are  generally  artificial  products ;  they  are  generally 
volatile,  and,  unless  their  equivalent  is  high,  they  are  liquid 
at  the  ordinary  temperature.  The  second  class,  which  in- 
cludes the  larger  number,  are  generally  products  of  vegetable 
life,  and  constitute  the  active  medicinal  principles  of  the 
plants  which  contain  them.  They  have  generally  a  powerful 
action  upon  the  animal  economy ;  the  volatile  alkaloids  of  the 
first  class  are  also  active  poisons.  Some  artificial  organic 
bases  have  been  produced  which  contain  sulphur  and  sele- 
nium, replacing  oxygen  ;  chlorine,  bromine,  and  the  residue 
of  nitric  acid  may  also  be  substituted  for  hydrogen  in  the 


ORGANIC    BASES,    OR    ALKALOIDS.  427 

constitution  of  these  bodies.  The  limits  of  this  work  will 
permit  us  to  notice  only  some  of  the  more  important  alkaloids 
of  the  above  classes. 

844.  Anilene,  C12H7N. — The  production  of  this  base  has 
been  already  described,  when  speaking  of  indigo  and   its 
derivatives.     Another  curious  process  for  its  production  has 
been   lately  discovered  by  M.  Hoffman :  when  nitrobenzene, 
(757,)  C,2H4NO4,  is  dissolved  in  alcohol  with  a  little  sulphuric 
acid,  and  fragments  of  iron  or  zinc  are  added  to  the  mixture, 
the  nascent  hydrogen  arising  from  the  solution  of  the  metal 
converts  the  nitrobenzene  into  anilene  and  water,  C12H4NO4 
-f  7H  =  4HO  +  C12H7N.      The  same  change   is   produced 
when  sulphureted   hydrogen  gas  is  passed   through  an  alco- 
holic   solution   of   nitrobenzene    previously    saturated   with 
ammonia.     The  gas  is  decomposed,  and   sulphur  separates 
in  a  crystalline   form,  while  anilene   remains   in    solution. 
Anilene  is  also  found  in  the  oil  of  coal-tar.     It  is  a  colorless, 
oily  liquid,  which  boils  at  328°,  and  has  a  density  of  18028 ; 
it  has  a   pleasant  vinous   odor,  and    burning  taste,   and   is 
highly  poisonous.     When  mixed  with  a  solution  of  bleaching 
powder,  (hypochlorite  of  lime,)  a  deep  violet-blue  color  is 
produced,  which  enables  us  to  detect  the  smallest  trace  of 
this  alkaloid.     Anilene  is  a  strong  base,  and  decomposes  the 
salts  of  zinc  and  iron,  precipitating  their  hydrated  oxyds ;  its 
salts  crystallize  beautifully.     When  the  oxalate  of  anilene  is 
exposed   to  heat,  it  loses  the  elements  of  water,  and  is  con- 
verted into  oxanilide,  which  corresponds  precisely  to  oxa- 
mide,    (698,)    and    by   the   action   of    alkalies    and    acids 
regenerates  oxalic    acid  and  anilene.      The   other  salts   of 
anilene  form  similar  compounds,  which  are  quite  analogous 
to  the  amides,  and  are  designated  by  the  name  of  anilides. 

845.  The  formation  of  chlor anilene ,    C12  (H6Cl)  N,    and 
bichlor  anilene,   C12(H5C12)N,  with   the    corresponding    bro- 
mine compounds,  has   been   already  alluded  to.     They  are 
crystalline  solids  and  act  as  bases,  but  less  energetically  than 
anilene.     Binitrobenzene,  which  may  be  regarded  as  nitroben- 
zene, in  which  two  more  equivalents  of  hydrogen  have  been 
replaced  by  the  residue  of  nitric  acid,  NHO6 — O2,  yields  by 
the  action  of  sulphureted  hydrogen  fine  yellow  prisms  of  a 
new  organic  base,  named   nitraniline,  which   is   C,2H6N2O4 
anilene,  in  which  NHO4  replaces  H2,  thus  C12(H4,NHO4)N. 
The  final  product  of  strong  nitric  acid  upon  anilene,  is  nitro- 
phenisic   acid ;    with   a    mixture   of  chlorate   of  potash  and 
hydrochloric  acid  it  forms  chloranile. 


'4-28  ORGANIC    CHEMISTRY. 

846.  Quinoline,  C,8H7N. — This  base  is  formed  when  the 
oxygenized  alkaloids  cinchonine,  quinine,  or  strychnine  are 
distilled    with    hydrate   of  potash  ;  thus,  one  equivalent  of 
quinine,   Gy  I^O4  +  4HO  =  2L\SH7N  +  4CO2+14H.     It   is 
identical  with  the  alkaloid  which  is  associated  with  anilene  in 
coal-tar,  and  which   has   been   described   under  the  name  of 
leukol.     Quinoline   is  an  oily  liquid,  with  a  powerful  odor, 
and  is  very  poisonous. 

847.  Nicotine,  C,0H7N. — This  alkaloid  is  obtained  by  dis- 
tilling a  concentrated  infusion  of  tobacco  with  lime  or  hydrate 
of  potash.     The  recent  plant  contains  a   peculiar  crystalline 
body,  called  nicotianine,  which  affords  nicotine  by  the  action 
of    caustic  potash,  but  it  is  probable  that  in   the   prepared 
tobacco   nicotine  exists    ready  formed.      When    tobacco    is 
smoked   in  a  German   pipe,  the  liquid  which   condenses  in 
the  long  stem,  contains  a   large   quantity   of  this   alkaloid. 
Nicotine  is  an  oily  liquid,  heavier  than  water  ;  it  has  a  burn- 
ing taste,  with  the  odor  of  tobacco,  and  is  an  active  poison. 

848.  Conine,  C16IIISN. — This   base  exists   in  all  parts  of 
the  Conium  maculatum,  but  most  abundantly  in  the  seeds;  it 
is  extracted  by  distilling  the  infusion  with  a  dilute  solution  of 
potash.     Like  the    preceding    bodies,    it    is    an    oily   liquid, 
which  possesses   strong  alkaline   properties.     It   has   a  disa- 
greeable taste  and  odor,  and  is  very  poisonous,  possessing  in  a 
high  degree  the  medicinal  powers  of  the  conium. 

849.  Amarine  or  Benzeline,  C42III8N2. — When  hydroben- 
zamido,    (754,)    is    boiled    with  a   dilute  solution   of  potash 
it   dissolves,   and    on  cooling,   crystals  of  amarine   (benzo- 
lene  of  Fownes)  separate.     It  has  the  same  composition  and 
the  same  equivalent  as  the  hydrobenzamide,  but   is  a  strong 
base.     The  same  alkaloid  is  formed  by  the  action  of  ammo- 
nia upon  an  alcoholic  solution  of  bitter  almond  oil. 

By  a  similar  process  to  that  by  which  nitrobenzene  yields 
anilene,  many  nitric  species  of  hydrocarbons  afford  peculiar 
bases,  which,  like  the  preceding,  contain  one  equivalent  of 
hydrogen  and  no  oxygen. 

850.  Alkaloids  of  Cinchona,  or  Peruvian  Bark. — The 
barks   of  several   species  of  cinchona  owe  their  medicinal 
properties  to  the  presence  of  two  alkaloids  which  are  named 
quinine  and   cinchonine.     They  are  extracted   bV  digesting 
the  bark  in  dilute  acid,  and  adding  to  the  infusion  a  solution 
of  carbonate  of  soda,  which  precipitates  the  alkaloids  in  an 
impure  state.     The  precipitate  is  washed   and  dissolved  in 


ORGANIC    BASES,    OR    ALKALOIDS.  429" 

boiling  alcohol ;  a  little  animal  charcoal  is  added  to  remove 
some  coloring  matter,  and  the  filtered  liquid,  on  cooling,  de- 
posits crystals  of  cinchonine,  while  the  more  soluble  quinine 
is  obtained  by  evaporation.  Quinine  is  a  white  crystalline 
substance,  sparingly  soluble  in  water,  but  readily  so  in 
alcohol  and  ether.  It  dissolves  in  acids,  and  forms  with  them 
crystallizable  salts,  which  are  very  bitter.  The  sulphate  and 
hydrochlorate  are  much  employed  in  medicine.  The  formula 
for  this  alkaloid  is  C40H24N2O4.  Cinchonine  resembles  quinine 
in  its  properties,  but  is  less  soluble  in  alcohol  and  ether ;  like 
that  alkaloid  it  is  employed  as  a  febrifuge.  Its  composition 
is  C^H^N^,  differing  from  quinine  only  by  two  equivalents 
of  oxygen. 

In  addition  to  these,  two  other  alkaloids,  aricine  and 
cinchoratine,  have  been  observed  in  different  species  of  cin- 
chona, but  they  are  little  known.  The  alkaloids  in  cinchona 
bark  are  combined  with  a  peculiar  bibasic  acid  called  the 
kinic  ;  its  composition  is  C14H12O12. 

851.  Alkaloids  of  Opium. — This  substance  is  the  inspis- 
sated juice  of  the  capsules  of  a  species  of  poppy,  Papaver 
somniferum,  and  contains  several  organic  bases.     The  most 
important  of  these,  and  the  one  to  which  it  owes  its  power  as 
an  anodyne,  is  morphine.     It  is  prepared  by  precipitating  a 
solution  of  opium  by  carbonate  of  soda,  as  in  the  process  for 
quinine ;  the  impure  morphine  is  digested  in  cold  alcohol  to 
remove  some  other  alkaloids  present,  and  finally  dissolved  in 
dilute  acetic  acid.     The  cautious  addition  of  ammonia  to  the 
acetate  thus  formed,  precipitates  the  morphine,  which  is  dis- 
solved in  hot  alcohol,  and  crystallizes  on  cooling.     It  forms 
brilliant  rectangular  prisms,  which  are  sparingly  soluble  in 
water,  readily  so  in  hot  alcohol,  and  insoluble  in  ether ;  it 
has   a    persistent   bitter   taste.     Its    formula   is   C^H^NO. 
Morphine  forms  crystalline  salts,   some   of  which,   as   the 
hydrochlorate,  sulphate,  and  acetate,  are  much  employed  in 
medicine.     The  best  opium  contains  six  or  eight  per  cent,  of 
this  alkaloid. 

852.  Codeine  is  a  base  which  occurs  in  small  quantities 
with  morphine ;  it  is  more  soluble  in  water  than  that  alkaloid, 
and  dissolves  readily  in  ether.     It  seems  allied  to  morphine 
in  its  effects  upon  the  animal  system.     The  composition  of 
codeine  is  C^EL^NC^. 

Narcotine. — This  alkaloid  is  found  in  considerable  quan- 
tities in  opium ;  it  is  separated  from  the  preceding  by  being 


4-30  ORGANIC    CHEMISTRY. 

very  soluble  in  ether,  and  insoluble  in  water.  It  is  a  feeble 
base ;  the  formula  of  narcotine  is  C46H25NOU.  When  heated 
with  a  mixture  of  sulphuric  acid  and  peroxyd  of  manganese, 
it  combines  with  four  equivalents  of  oxygen,  and  is  decom- 
posed into  a  peculiar  nonazotized  acid  called  the  opianic,  and 
a  new  alkaloid,  cotarnine,  which  is  C^H^NC^. 

In  addition  to  those  already  mentioned,  opium  contains 
three  other  bases  in  small  quantity ;  they  are  named  thebaine, 
pseudomorphine,  and  narceine  ;  but  little  is  known  of  them. 
It  affords  also  a  peculiar  tribasic  acid  which  is  called  the 
meconic  ;  its  formula  is  C,4H4OI4 ;  the  morphia  exists  in  the 
juice  of  the  poppy  combined  with  meconic  and  sulphuric 
acids. 

853.  Strychnine. — This  alkaloid  is  found  in  the  Strychnos, 
nux-vomica,  and  several  other  plants  of  the  same  genus.     It 
is  prepared  by  digesting  the  nux-vomica  with  water  acidulated 
by  sulphuric  acid,  and  precipitating  the  solution  by  caustic 
lime.     The    impure   precipitate   is    boiled  with   alcohol  and 
animal  charcoal,  and  the  liquid  on  cooling  deposits  the  strych- 
nine in  crystals.     It  is  almost  insoluble  in  water,  absolute 
alcohol,  and  ether,  but  dissolves  in  dilute  alcohol ;  its  salts 
are  intensely  bitter  and  highly  poisonous.     Strychnine  and 
its  compounds  produce  a  spasmodic  affection  of  the  muscles 
of  voluntary  motion  in  cases  of  paralysis ;  they  are  used  in 
minute  doses  with  great  benefit.    The  poison  of  the  celebrated 
Upas   is    the    product  of  the   Strychnos   ticute,  and   owes 
its  activity  to  strychnine.     The   formula   for  strychnine  is 
C44Ht4N2O4 ;    when   fused   with   hydrate  of  potash   it  yields 
quinoleine.     Brucine  is  another  organic  base  which  is  asso- 
ciated with  the  last  in  several  species  of  Strychnos ;  it  re- 
sembles it  in  its  characters,  but  is  somewhat  less  active  as  a 
poison. 

854.  Solanine,  from  the   Solanum  nigrum,  and   several 
other    species,    Hyoscyamine,    from     Hyoscyamus     niger, 
Atropine,   from   Atropa    belladonna,   and    Daturine,   from 
Datura  stramonium,  are  alkaline  principles  which  possess  in 
great  perfection  the  poisonous  properties  of  the   plants  from 
which   they  are  derived.     They  are  obtained   by  somewhat 
complicated  processes,  and  are  crystalline  and  volatile.    Their 
salts  are  employed  in  medicine. 

855.  Veratrine  is    found    in    the    Veratrum  album,  and 
some  other  species  of  the  same   genus ;    it   forms  a  white 
crystalline  powder,  which  is  insoluble  in  water,  but  soluble 


OTHER    VEGETABLE    PRINCIPLES.  431 

in  alcohol.  It  is  a  powerful  acrid  poison,  but  is  used 
medicinally  in  neuralgia  with  beneficial  results.  Aconitine 
is  obtained  from  the  Aconitum  napellus,  and  resembles 
veratrine  in  its  properties.  Sanguinarine  is  an  alkaloid 
which  exists  in  the  blood-root,  Sanguinaria  canadensis,  and 
to  which  this  plant  owes  its  active  properties.  Emetine,  the 
emetic  principle  of  ipecacuana,  and  capsicine,  to  which  the 
pungency  of  cayenne  pepper  is  due,  are  also  organic  bases. 

856.  Theine;  Caffeine,  CI6H10N4O4.— This  organic  base 
is  found  in  coffee,  tea,  the  fruit  of  the  Paulinia  subalis,  and 
the    Ilex    paraguayensis,    which    affords    ihc    matte,    or 
Paraguay   tea.     It  is   most  abundant  in   green   tea,   which 
contains  from  two  to  five  per  cent. ;  the  best  coffee  does  not 
yield  one  per  cent.     To  obtain  it,  a  strong  decoction  of  the 
leaves  is   mixed  with  a  solution   of  the  surbasic  acetate  of 
lead,  as  long  as  a  precipitate  is  formed ;  to  the  clear  solution 
a  little  ammonia  is  added,  to  precipitate  the  excess  of  lead, 
and  the  liquid   by  evaporation   furnishes  theine   in  delicate 
silky  crystals.     It  is  readily  soluble  in  hot  water  and  alcohol, 
and  may  be  volatilized  without  decomposition ;   its  taste  is 
slightly   bitter.     Theine  is  a  feeble  base,  and   its  salts  arc 
easily  decomposed  ;  the  hydrochlorate  crystallizes  beautifully. 

857.  It  is  worthy  of  notice,  that  the  plants  which  furnish 
this   alkaloid   are    used    by  different   nations    to   prepare   a 
grateful   and    gently   stimulating   beverage.     As  these  sub- 
stances resemble  each  other  only  in  containing  theine,  it  is 
probable   that   they   owe    their   common    properties    to   the 
presence   of   this    principle,    and    that,   in    some    unknown 
manner,  it  promotes   digestion  and   the  other  vital  functions. 
The  Brazilians  prepare  from  the  fruit  of  the  Paulinia  subalis 
an  extract  called  by  them  guarana,  which  is  much  esteemed 
as   a    remedy    in   dysentery    and    nephritic   complaints ;    it 
contains  a  considerable  quantity  of  theine. 

The  seeds  of  cocoa,  Theobroma  cacao,  contain  a  crystal- 
line substance,  somewhat  analogous  to  theine.  It  is  called 
theobromine,  and  has  the  formula  C18H10N6O4.  It  does  not 
seem  to  possess  alkaline  properties. 

OTHER    VEGETABLE    PRINCIPLES. 

858.  Besides  those  already  described  under   the  previous 
heads,  there  are  a  great  number  of  neutral  crystalline  prin- 
ciples which  have  been  extracted  from  vegetates.     Among 


4-32  ORGANIC    qHEMISTRY. 

them  are  a  few  whose  reactions  have  been  studied,  that 
exhibit  a  remarkable  tendency  to  decomposition,  under  the 
influence  of  ferments  and  other  agents.  Under  this  class 
may  be  included  amygdaline,  asparagine,  salicine,  and  phlo- 
riclzine. 

859.  Amygdaline. — This  principle  is  contained   in   bitter 
almonds,  and  peach  kernels.     It  is  prepared  by  pressing  the 
bruised  almonds  between  heated  plates  to  separate  the  fat  oil, 
and  boiling  the  residue  in  strong  alcohol.     The  alcohol  is  then 
distilled  off  in   a  water-bath,  and   the  syrupy  residue  mixed 
with  a  little  yeast  is  set  aside  to  ferment ;  by  this  treatment 
a  portion  of  sugar  which   the   almonds  contain  is  destroyed. 
The  clear  liquid  is  again   evajMjrated   to   a   syrup  and  mixed 
with  ether,  which  precipitates  the  amygdaline  in  a  crystalline 
powder.     It   is    readily  soluble    in    alcohol   and  water,  and 
crystallizes  from  the  latter  solvent   in   large  prisms,  with  six 
equivalents  of  water ;  it  lias  a  bitter  taste.     The  formula  of 
amygdaline  is  C^H^NOn  ;   when  boiled  with  water  of  baryta, 
it  takes  up  the  elements  of  two  equivalents  of  water,  and  is 
converted  into  ammonia  and  amygdalic  acid,  which  remains 
dissolved  as  amygdalate  of  baryta  ;  its   formula  is  C^II^Oi-i. 
Amygdaline  may  be  regarded  as  the  amide  of  this  peculiar 
acid. 

This  principle  exists  in  bitter  almonds,  in  the  proportion 
of  four  or  five  per  cent. ;  besides  this,  they  contain  an 
albuminous  matter,  which  has  some  analogy  to  animal 
albumen,  and  it  is  called  emuliine,  or  synaptase  ;  it  consti- 
tutes the  great  part  of  sweet  almonds,  which  contain  no 
amygdaline.  When  a  solution  of  amygdaline  is  mixed  with 
about  one-tenth  part  of  emulsine,  a  decomposition  ensues,  and 
in  a  few  minutes  the  amygdaline  is  completely  converted  into 
bcnzoilol,  prussic  acid  and  grape  sugar.  One  equivalent  of 
amygdaline  and  four  of  water,  contain  the  elements  of  one 
equivalent  of  benzoiloi,  one  of  prussic  acid,  and  two  of  grape 
sugar,  C^NO^-MHO  =  CUH<,O2  +  C2IIN  +  2CI2H12O12. 
The  action  of  emulsine  in  this  singular  decomposition,  is  analo- 
gous to  that  of  a  ferment ;  if  exposed  to  a  heat  of  212°,  it 
coagulates,  becomes  insoluble,  and  loses  the  power  of  effect- 
ing the  change. 

860.  Asparagine. — This  substance  is  found  in  the  stalks 
of  asparagus,  the  roots  of  marsh-mallows,  beets,  and  many 
other  plants,  and   separates  in  a  crystalline  form  from  the 
concentrated  juice  or  decoction.    It  crystallizes  in  transparent 


OTHER   VEGETABLE    PRINCIPLES.  433 

rhombic  prisms,  of  a  fresh  and  somewhat  nauseous  taste ;  it 
is  sparingly  soluble  in  cold,  but  more  readily  in  boiling  water. 
The  formula  for  asparagine  is  C8H8N2O6.  Asparagine  is  the 
amide  of  a  peculiar  acid  called  the  aspartic  ;  by  the  action 
of  dilute  alkalies  or  acids  it  assumes  the  elements  of  water, 
and  yields  aspartic  acid  and  ammonia,  C8H8N2O6-f  2HO= 
C8H7NO8-f  NH3.  The  aspartic  acid  is  crystallizable  and 
sparingly  soluble  in  water;  it  is  an  acid  amide,  (697.) 
When  boiled  for  some  time  with  hydrochloric  acid  or  a 
solution  of  potash,  it  is  converted  into  ammonia  and  a  new 
acid  which  has  not  yet  been  examined.  When  a  solution  of 
impure  asparagine  is  exposed  to  the  air  it  undergoes  a  kind 
of  fermentation,  and  after  some  time  the  liquid  contains 
nothing  but  neutral  succinate  of  ammonia.  An  equivalent 
of  asparagine  with  four  of  water  contains  the  elements  of 
one  equivalent  of  the  succinate  of  ammonia,  and  two  of 
oxygen;  but  the  reaction  is  not  understood,  and  is  probably 
more  complex. 

861.  Salicine. — This  principle  exists  in  the  bark  of  those 
species  of  willow  which  have  a  bitter  taste.     The  decoction 
of  the  bark  is  mixed  with  the  surbasic  acetate  of  lead  as  long 
as  a  precipitate  is  formed ;  to  the  filtered  liquid  dilute  sul- 
phuric acid  is  added  to  precipitate  the  dissolved  lead,  carefully 
avoiding  an  excess.     The  solution  is  then  decolorized  by 
animal  charcoal,  and,  by  evaporation  and  cooling,  deposits 
pure  salicine.    It  is  so  abundant  in  the  bark  of  some  willows 
as  to  separate  in  crystals  when  a  concentrated  decoction  is 
cooled.     Salicine  forms  small  white  crystals,  readily  soluble 
in  alcohol  and  water ;  it  has  a  very  bitter  taste,  and  is  em- 
ployed in  medicine  as  a  febrifuge  and  tonic.     Its  formula  is 

C^H^OH. 

862.  When  a  solution  of  salicine  is  mixed  with  a  portion 
of  the  emulsine  of  sweet  almonds,  and  exposed  for  some 
hours  to  a  heat  of  105°  F.,  it  is  completely  decomposed  into 
grape  sugar  and  a  new  compound,  saligenine,  which  sepa- 
rates in  fine  rhombohedral  crystals.    Its  composition  is  repre- 
sented by  C14H8O4.     One  equivalent  of  salicine  and  two  of 
water  contain  the  elements  of  one  equivalent  of  grape  sugar 
and  one  of  saligenine,  Ca6H18OI4_+ 2HO=C12H12O12  +  C14H8O4. 
Saligenine  is   readily  soluble  in  water,  alcohol,  and  ether; 
dilute  acids  convert  it  into  a  white  insoluble  matter  which  is 
named  saliretine,  which  is  formed  from  it  by  the  loss  of  the 
elements  of  two  equivalents  of  water.     When  a  solution  of 

37 


ORGANIC    CHEMISTRY. 

saligenine  is  mixed  with  chromic  acid  it  loses  two  equivalents 
of  hydrogen  and  is  converted  into  salicylol,  (759 ;)  the  same 
change  is  effected  by  oxyd  of  silver,  which  is  reduced  to  the 
metallic  state. 

863.  When  a  solution  of  salicine  in  dilute  sulphuric  or 
hydrochloric  acid  is  heated,  it  is  first  decomposed  into  grape 
sugar  and  saligenine,  but  the  farther  action  of  the  acid  con- 
verts the  latter  into  saliretine,  which  separates  in  white  flakes. 

A  mixture  of  salicine  with  dilute  sulphuric  acid  and  bichro- 
mate of  potash  affords,  by  distillation,  a  large  quantity  of 
salicylol.  Boiling  dilute  nitric  acid  decomposes  it ;  first  con- 
verting the  saligenine  into  salicylol,  and  then  into  nitro- 
salicylic  acid  ;  if  the  acid  is  concentrated  the  final  product  is 
the  nitrophenisic  acid,  accompanied  with  oxalic  acid  formed 
from  the  sugar.  A  mixture  of  hydrochloric  acid  and  chlorate 
of  potash  converts  it  into  chloranile ;  when  fused,  potash 
salicinc  yields  a  large  quantity  of  salicylic  acid. 

864.  If  salicine   is  dissolved   in   cold,   very   dilute   nitric 
acid,  it  gradually  deposits  crystals  of  a  new  substance  called 
helicine.     Its  composition  is  expressed  by  CsllnOKJ  and  it  is 
formed  from  salicinc  by  the  addition  of  two  equivalents  of 
oxygen,  and   the  separation  of  one  of  water.     Under  the 
influence   of    emulsine,    it    takes    up    the   elements   of   one 
equivalent  of  water,  and   is  resolved   into  grape  sugar  and 
salicylol,  C26IInOl5H-IIO=CuH6O4  +  C,2H1A2;   dilute  acids 
cause  the  same  decomposition. 

865.  Phloridzine. — This  principle  is   found  in  the  root- 
bark  of  the  apple,  pear,  cherry,  and   some  other  trees.     A 
concentrated   decoction  of  the  apple   root-bark  deposits,  by 
cooling,  a    brown   crystalline    powder,   which    may   be  de- 
colorized   by   animal    charcoal.       It    forms    delicate    silky 
crystals,    which    are   almost    insoluble    in    cold    water,    but 
readily  soluble  in  hot  water  and  alcohol.     It  is  bitter,  and  a 
febrifuge,  and   has  been  employed  medicinally.     The  com- 
position of  phloridzine  may  be  expressed  by  C^I^O^ -f  2aq. 
If  boiled  with  dilute  acids  it  is  converted   into   grape  sugar, 
and   an   insoluble  compound   called  phloretine,  C.J,H14OI2  + 
4HO=C12H12012+C12H604. 

When  phloridzine  is  exposed  to  the  action  of  moist  air 
and  ammonia,  it  is  gradually  changed  into  a  very  soluble 
blue  compound.  From  the  solution  of  this,  acetic  acid  pre- 
cipitates a  red  powder  called  phloridzeine,  which  dissolves  in 
ammonia  with  a  splendid  blue  color.  It  is  derived  from 


THE  CYAN1DS,  AND  COMPOUNDS  DERIVED  FROM  THEM.  435 

phloridzine,  by  the  addition  of  the  elements  of  one  equivalent 
of  ammonia  and  four  of  oxygen,  with  the  separation  of  one 
of  water.  This  reaction  is  analogous  to  that  by  which 
orceine  is  formed  from  orcine,  (830.) 


THE    CYANIDS,  AND    THE    COMPOUNDS    DERIVED    FROM    THEM. 

866.  The  cyanids  do  not   exist  in   nature,   but  are  ex- 
clusively artificial  products.     When  any  organic  substance 
containing  nitrogen   is   heated  with  potassium,  a  cyanid  of 
potassium  is   formed,   and  the  same  result   is   obtained   if 
caustic  potash  is  used,  provided   this   is  not  in  excess.     If 
nitrogen  gas  is  passed  over  a  mixture  of  carbonate  of  potash 
and  charcoal  heated  to  bright  redness,  it  is  absorbed,  and  a 
cyanid  is  formed ;  the  same  result  is  afforded  by  ammonia. 
The  formula  of  cyanid  of  potassium   is  C2KN,  and  it  may 
hence  be  formed  from  the  direct  union  of  the   potassium 
reduced  by  the  carbon,  with  the  nitrogen  and  carbon  present. 

867.  Hydrocyanic  Acid;  Prussic  Acid,  C2HN. — This 
acid  is  obtained  by  distilling  cyanid  of  potassium  with  dilute 
sulphuric  acid ;  but  a  more  elegant  process  is  to  decompose 
cyanid  of  mercury  by  sulphureted  hydrogen,  C2HgN-|-HS 
—  HgS-f  C2HN.     The  reaction  is  aided   by  a  gentle   heat, 
and  the  pure  acid  distils  over ;  it  must  be  collected   in  a 
cool  receiver.     Hydrocyanic  acid  is  a  colorless,  limpid  liquid, 
which  has  a  specific  gravity  of  *697,  and  boils  at  80°.     It  is 
very  combustible,  and   burns  with  a  white  flame ;  it  scarcely 
reddens  litmus  paper.     The  taste  of  this  substance  is  pungent 
and  disagreeable,  and  its  odor  very  powerful,  recalling  that 
of  peach   blossoms   or   bitter   almonds :   the   latter    owe  a 
portion  of  their  peculiar  flavor  to  this  acid,  which,  as  has 
been   before  stated,  is  one  of  the   products  of  the  decom- 
position of  amygdaline  by  ernulsine,  and  constitutes  a  part 
of  the  crude  bitter  almond  oil. 

868.  Hydrocyanic  acid  is  one  of  the  most  fatal  poisons 
known  ;    a  single  drop   of  the  pure  acid,  placed    upon   the 
tongue  of  a  large  dog,  produces  immediate  insensibility  and 
death  ;  and  the  diluted  acid  in  even  very  small  doses,  causes 
giddiness,  often  followed  by  nausea.     It  appears  to  act  as  a 
sedative  to  the  arterial  system,  and  the  suspension  of  anima- 
tion following  a  poisonous  dose  of  it,  does  not  always  result 
in  death   if  proper  stimulants   are   employed ;    ammonia  is 
generally  considered  as  the  most  efficient  antidote  to  its  effects. 


436  ORGANIC    CHEMISTRY. 

The  vapor  of  the  concentrated  acid  is  very  poisonous,  but  when 
considerably  diluted  with  air,  does  not  appear  to  be  so  dele- 
terious as  has  been  generally  supposed.  In  the  process  of 
the  arts,  it  is  frequently  evolved  in  considerable  quantities, 
yet  the  workmen  who  are  constantly  exposed  to  it,  experience 
no  injurious  effects.  The  diluted  acid  is  much  employed  in 
medicine.  When  pure  it  soon  decomposes  spontaneously  ; 
but  if  diluted,  and  especially  if  a  small  quantity  of  sulphuric 
acid  is  present,  it  may  be  preserved  for  a  long  time. 

809.  When  the  vapor  of  formiate  of  ammonia  is  passed 
through  a  tube  heated  to  400°,  it  is  completely  decomposed 
into  prussic  acid  and  water,  C2H2O4,NH3=4lIO-r-C2HN. 
The  cyanids,  in  the  presence  of  a  strong  acid,  take  up  again 
the  elements  of  water,  and  regenerate  formic  acid  and  ammo- 
nia ;  alkalies  cause  the  same  decomposition ;  a  solution  of 
cyanid  of  potassium  is  decomposed  by  boiling.  Ammonia  is 
evolved,  and  formiate  of  potash  is  formed.  Hydrocyanic 
acid  is  then  to  be  regarded  as  an  amide  of  formic  acid, 
differing  from  the  ordinary  amides  of  monobasic  acids  in 
leing  formed  by  the  abstraction  of  four  equivalents  of  water. 
Witli  metallic  oxyds,  hydrocyanic  acid  yields  cyanids  and 
water. 

870.  Cyanid  of  Potassium. — This  is  formed  by  the  action 
of  potash  upon  animal  matters,  but  in  this  way  is  always  im- 
pure. It  is  obtained  pure  by  saturating  an  alcoholic  solution 
of  potash  with  hydrocyanic  acid,  or  by  decomposing  the  ferro- 
cyanid.  This  salt,  well  known  in  the  arts  as  yellow  prussiate 
of  potash,  contains  the  elements  of  two  equivalents  of  cyanid 
of  potassium  and  one  of  cyanid  of  iron.  When  it  is  heated 
to  redness  in  a  close  vessel,  the  cyanid  of  iron  is  decomposed 
into  nitrogen  and  a  carburet  of  iron,  and  pure  cyanid  of  potas- 
sium remains;  the  mass  is  boiled  with  alcohol,  which  deposits 
the  cyanid  on  cooling,  in  cubical  crystals.  It  is  very  soluble 
and  deliquescent,  and  has  an  alkaline  reaction.  Its  taste  is 
caustic,  at  the  same  time  resembling  that  of  prussic  acid,  and 
it  is  highly  poisonous.  Its  aqueous  solution  smells  of  hydro- 
cyanic acid  ;  it  cannot  be  kept  in  this  state,  as  it  is  gradually 
converted  into  formiate  of  potash,  with  the  evolution  of 
ammonia. 

The  cyanid  of  potassium  is  of  great  use  in  chemical 
analysis,  particularly  as  a  reducing  agent,  in  which  it  is 
inferior  only  to  potassium ;  if  the  cyanid  is  fused  in  a  cruci- 
ble, and  oxyd  of  copper  is  added  to  it,  the  latter  is  reduced 


THE  CYANIDS,  AND  COMPOUNDS  DERIVED  FROM  THEM.  437 

with  ignition ;  the  oxyds  of  lead  and  iron,  and  even  their  sul- 
phurets  are  reduced  in  the  same  way,  at  a  temperature  below 
redness. 

871.  The  cyanids  of  the  metals  are  generally  insoluble  in 
water,  but   soluble   in   an   excess   of  cyanid   of  potassium. 
The  cyanid  of  mercury,  C2HgN,  is,  however,  soluble  and 
crystallizable.     It   is   formed  by  boiling  two    parts   of  the 
yellow  prussiate  of  potash  with  three  of  sulphate  of  mer- 
cury in  fifteen  of  water  for  a   few  minutes ;  on  cooling  the 
cyanid  crystallizes.     It  is  readily  soluble  in  water  and  alco- 
hol, has  a  nauseous   metallic  taste,  and   is   very  poisonous. 
The  cyanid  of  silver,  C2AgN,  is  a  white  insoluble  precipitate, 
resembling  the  chlorid. 

The  action  of  chlorine  upon  hydrocyanic  acid  or  cyanid 
of  mercury  yields  a  gaseous  compound,  in  which  chlorine 
replaces  the  hydrogen.  Its  composition  is  C2C1N.  This 
gas  has  a  pungent  and  disagreeable  odor,  and  is  absorbed  by 
water  without  decomposition.  The  action  of  bromine  and 
iodine  upon  the  cyanid  of  mercury  yields  crystalline  com- 
pounds which  correspond  to  the  last.  They  are  volatile  and 
poisonous.  These  substances  are  generally  described  as 
chlorid,  bromid,  and  iodid  of  cyanogen. 

872.  Cyanogen. — When    cyanid   of   mercury   is   heated 
nearly  to  redness,  it  is  decomposed  into  metallic  mercury  and  a 
colorless  inflammable  gas,  to  which  the  name  of  cyanogen  is 
given.     The  decomposition  is  very   simple,  C2HgN=Hg-f 
C2N.     This   gas    has   a    pungent  odor,  resembling  that  of 
prussic  acid,  and  burns  with  a  very  rich  purple  violet  flame, 
yielding  carbonic  acid  and  nitrogen.     It  is  soluble  in  water 
and  alcohol,  and  for  this  reason   must  be  collected  over  mer- 
cury.     Its  density  is  1'8026,  and  it   is   composed   of  two 
equivalents,  or  one  volume  of  carbon  vapor,  and  one  volume 
of  nitrogen,  condensed    into   one   volume,  8320 +  -9-706= 
1'8026,  or  one  volume  of  cyanogen. 

When  potassium  is  heated  in  cyanogen  gas,  union  takes 
place  with  the  evolution  of  heat  and  light,  and  cyanid  of 
potassium  is  formed.  Many  chemists  regard  cyanogen  as 
allied  to  chlorine  in  its  characters  and  possessing,  although  a 
compound,  the  reactions  of  an  element.  The  cyanid  of  po- 
tassium is  upon  this  view  assimilated  to  the  chlorid  of  the 
same  metal,  and  the  prussic  acid  is  considered  as  a  compound 
of  cyanogen  with  hydrogen,  analogous  to  hydrochloric  acid. 
These  two  bodies  will  not,  however,  combine  under  any  cir- 
37* 


438  ORGANIC    CHEMISTRY. 

cumstanccs,  nor  does  cyanogen  act  upon  organic  bodies 
replacing  their  hydrogen,  so  that  the  analogies  by  which  this 
theory  is  supported  are  but  very  imperfect. 

873.  When  cyanogen  unites  directly  with  sulphureted 
hydrogen,  its  equivalent  is  represented  by  two  volumes,  so 
that  its  formula  must  be  doubled,  and  the  real  composition  of 
the  gas  is  hence  C4N2. 

Hydrocyanic  acid  and  the  cyanids  react  upon  many  or- 
ganic matters  which  contain  oxygen  or  chlorine ;  the  hydro- 
gen or  metal  unites  with  these,  substituting  in  their  places  the 
residue  C2N.  Thus  hydrochloric  ether,  C4H6C1  +  C2KN  = 
KCl-f-C4lI5C2N,  or  C6H5N ;  these  compounds  are  but  little 
known. 


CYANATES. 

874.  These  salts  are  formed   by  the  direct  oxydation  of 
the  cyanids  ;  when  oxyd  of  lead  is  added  to  fused  cyanid  of 
potassium,  the  metal   is   reduced,  and  cyanate  of  potash  is 
formed,  C2KN  +  2PbO=2Pb  +  C2KNO2.     The  cyanic  acid, 
C2HNO2,  cannot  be  obtained  from  the  cyanates  by  a  stronger 
acid,  as  it  immediately  combines  with  the  elements  of  water 
and  is  resolved  into  carbonic  acid  and  ammonia,  C2HNO2-f 
2HO=2CO2  +  NH3.     The  aqueous  solution  of  the  cyanate 
of  potash  undergoes  the  same  decomposition,  spontaneously 
evolving  ammonia  and  leaving  bicarbonate  of  potash.    Cyanic 
acid  may  hence  be  viewed  as  an  amide  of  carbonic  acid. 

875.  Cyanic  acid   is  obtained   by   the  dry  distillation  of 
cyanuric  acid,  which   is   polymeric  of  it,  and   contains  the 
elements  of  three  equivalents ;  the  product  is  condensed  in  a 
carefully  cooled  receiver,  and  is  a  colorless  liquid  of  a  pene- 
trating odor,  resembling  the  acetic  acid ;  it  is  very  corrosive 
to  the  skin,  and  causes  vesication  as  effectually  as  a  hot  iron. 
It  cannot  be  preserved  for  any  considerable  time,  but  changes 
into  a  white  insoluble   mass   like  porcelain,  which  is  called 
cyamelide,  and   has  the  same  composition  as  the  acid ;  but 
its  real  nature  is  not  known ;  by  heat  it  is  converted  again 
into  cyanic  acid. 

876.  Cyanate  of  Potash,  C2KNO2,  is  prepared  from  the 
cyanid  as  before  described,  or  more  cheaply  from  the  yellow 
prussiate  of  potash.     This  is  carefully  dried  at  212°,  mixed 
with   one-half  its    weight   of  peroxyd    of  manganese,    and 
heated   to  low  redness ;  the  mass  takes  fire  and   burns   like 
tinder;  the  residue  contains  cyanate  of  potash,  which  may 


CYANATES.  439 

be  extracted  by  boiling  alcohol ;  from  this  solution  it  crys- 
tallizes on  cooling.  The  cyanale  of  potash  crystallizes  in 
tables  resembling  chlorate  of  potash ;  it  is  very  soluble  in 
water,  but  the  solution  slowly  decomposes  into  carbonate  of 
potash  and  ammonia,  and  the  crystals  undergo  the  same 
change  in  moist  air. 

877.  The  vapor  of  cyanic  acid  combines  withthe   same 
monia  and  forms  a  crystalline  compound,  which  is  C2HNO2, 
2NH3.     This  is  readily  soluble  in  water,  and  possesses  the 
characters   of  a   cyanate ;    if   the   solution   is   boiled,   one 
equivalent  of  ammonia  is  expelled,  and   there  remain  the 
elements   of   the    neutral    cyanate,    C2HNO2,NH3,   but   by 
evaporation  crystals  of  a  new  substance  are  deposited,  which 
has   none   of  the  characters   of  a   salt.      It   contains   the 
elements  of  cyanate  of  ammonia,  but,  unlike  the  cyanates, 
unites  directly  with  the  acids  to  form  definite  compounds. 
This   singular   substance   is    contained    in   large   quantities 
in   urine,   and  is   hence   named  urea.      It   is   obtained  by 
evaporating  fresh  urine   at  a  heat  below   212°  to  a  small 
bulk,  and  mixing  the  residue  with  nitric  acid.     The  nitrate 
of  urea,  which    is   sparingly  soluble   in  dilute   nitric   acid, 
separates  in  pearly  plates,  which  are  washed  in  cold  water 
and  decomposed  by  carbonate  of  potash.     The  nitfate  of 
potash  is  separated   by  crystallization  from  the  more  soluble 
urea,    which   is    finally    purified    by   crystallizing   it   from 
alcohol. 

878.  A  better  process  is  to  decompose  the  cyanate  of 
potash   by  a  salt  of  ammonia ;  twenty-eight   parts  of  dried 
prussiate  of  potash  are  roasted  with  oxyd  of  manganese  as 
before  described,  and  the  cyanate,  dissolved  from  the  mass 
by  washing  with   cold   water,  is  mixed  with  twenty-and-a- 
half   parts   of  dry   sulphate   of  ammonia,    and   the    whole 
evaporated  to  dryness  in  a  water-bath.     Sulphate  of  potash 
and  cyanate  of  ammonia  are  first  formed,  and  this  last  is 
immediately  changed  into  urea ;  the  dry  mass  is  boiled  with 
alcohol,  which  dissolves  the  urea,  and  on  cooling  deposits 
it  in  crystals. 

879.  Urea  forms  transparent,  colorless,  four-sided  prisms, 
readily  soluble  in  water  and  alcohol ;  it  is  inodorous,  and  its 
taste  is  fresh  and  biting,  resembling  that  of  nitre.     The  basic 
powers  of  urea  are  very  weak,  but  it  yields  crystalline  com- 
pounds   with    hydrochloric,    nitric,  and   oxalic  acids.     The 
nitrate,  C2H4N2O2,NHO6,  forms  large  brilliant  plates,  which 


440  ORGANIC    CHEMISTRY. 

require  eight  parts  of  water  for  solution.  When  a  solution 
of  urea  is  evaporated  with  one  of  nitrate  of  silver,  the 
elements  re-arrange  themselves  to  form  nitrate  of  ammonia 
and  cyanate  of  silver. 

SULPHOCYANATES. 

880.  These  compounds  are  cyanates  in  which  the  oxygen 
is  replaced  by  sulphur,  and  are  much  more  stable  than  the 
previous  class.  When  cyanid  of  potassium  is  fused  with  a 
metallic  sulphurct  or  with  sulphur,  It  combines  with  two 
equivalents  and  forms  sulphocyanate  of  potash,  C2KNS2. 
The  sulphocyanic  acid,  C2HNS2,  is  obtained  by  decomposing 
the  sulphocyanate  of  lead  by  sulphuric  acid,  and  is  a  color- 
less, sour  liquid,  with  an  odor  like  vinegar.  It  is  not  poison- 
ous. The  sulphocyanate  of  potash  is  prepared  by  fusing 
in  an  iron  vessel  a  mixtu^  of  forty-six  parts  of  dry  prussiate  of 
potash,  seventeen  of  dry  carbonate  of  potash,  and  thirty-two 
of  sulphur.  The  vessel  is  kept  covered,  and  the  mixture 
occasionally  stirred  until  the  evolution  of  gas  has  ceased,  and 
the  heat,  which  should  be  gentle  at  first,  has  been  raised  to 
redness.  The  sulphocyanate  is  dissolved  out  of  the  black 
mass  by  boiling  water,  and  crystallizes  by  evaporation  and 
cooling.  It  forms  colorless  prismatic  crystals  of  a  sharp, 
cooling  taste,  like  nitre.  It  is  deliquescent,  and  very  soluble 
in  water  and  alcohol.  When  its  solution  is  heated  with 
nitric  acid,  and  chlorine  gas  is  passed  through  it,  a  yellow 
precipitate  is  formed,  which  was  formerly  regarded  as  a 
sulphuret  of  cyanogen,  but  it  contains  oxygen  and  hydrogen, 
and  its  composition  varies  exceedingly.  The  name  of 
cyanox sulphide  has  been  given  to  it ;  when  exposed  to  heat 
it  evolves  sulphur,  sulphuret  of  carbon,  and  several  other 
compounds,  and  leaves  a  grayish  yellow  residue  which 
Liebig  has  named  mellon.  Its  composition  is  C6N4 ;  when 
exposed  to  a  bright  red  heat,  it  is  resolved  into  cyanogen  and 
nitrogen  gases. 

When  sulphocyanate  of  ammonia  is  distilled,  it  is  decom- 
posed, affording  ammonia,  bisulphuret  of  carbon,  and  a  white 
powder  called  melam,  which  will  be  afterwards  described. 
A  mixture  of  muriate  of  ammonia  and  sulphocyanate  of  pot- 
ash  affords  the  same  products. 

The  soluble  sulphocyanates  are  characterized  by  striking  a 
deep  blood-red  color  with  persalts  of  iron.  The  color  is  so 


SULPHOCYAXATES.  44-1 

intense  that  these  substances  are  most  delicate  tests  for  each 
other.  The  seleniocyanates,  in  which  selenium  replaces  oxy- 
gen, are  similar  to  the  sulphocyanates. 

Results  of  the  complication  of  the  Cyanids. 

881.  The  cyanates  exhibit  a  strong  tendency  to  form  poly- 
meric bodies  by  the  union  of  three  or  more  molecules  of  the 
original  compound ;  and  thus  give  origin  to  a  new  class  of 
substances,  which  are  much  more  stable  than  the  preceding. 
When  hydrocyanic  acid  and  chlorine  fcare  mixed  and  exposed 
to  the  sun-light,  a  white  crystalline  matter  is  deposited  which 
contains  the  same  proportion  of  the  elements  as  the  gaseous 
compound  cfcscribed  under   hydrocyanic  acid ;  but  its  vapor 
has   three  times   the  density  of  this,  and  its  composition  is 
represented  by  C6C13N3.     When  its  alcoholic  solution  is  mixed 
with  one  of  ammonia,  it  takes  up  the  elements  of  six  equiva- 
lents of  water,  and  is  converted  into  hydrochloric  and  cyanic 
acids,  which   combine  with  the  ammonia,  C6CI3N3-f  6HO= 
C6H3N3O6  +  3HC1. 

882.  Cyan-uric   Acid. — This   acid   is   polymeric   of   the 
cyanic,  three  equivalents  of  which   unite  to  form  one  of  the 
cyanuric,  3C2HNO2— C6H3N3O6.    When  a  solution  of  cyanate 
of  potash  is   mixed  with   a  quantity  of  acetic  acid  sufficient 
to   decompose   two-thirds  of  it,  a   cyanurate   of   potash   is 
deposited.     Cyanuric  acid  is  readily  formed  by  the  decompo- 
sition   of  urea,   three   equivalents   of  which,   SC^E^NaC^^ 
C6H3N3O6+3NH3.     Pure  urea  is  maintained  in  a  state  of 
fusion    until   the   evolution   of  ammonia   ceases,  and   it   is 
changed   into  a  grayish  white  mass.     This  is  dissolved  in 
concentrated  sulphuric  acid,  and  nitric  acid  is  added  drop  by 
drop  until  the  solution  is  decolorized  ;  it  is  then  mixed  with 
its  bulk  of  water,  and  on  cooling  deposits  the  cyanuric  acid 
in  crystals.     It  is  inodorous,  and  has  a  feebly  acid  taste ;  it 
may  be  dissolved  in  strong  acids  without  change,  but  when 
long  boiled  with  them   is  decomposed,  like  the  cyanic,  into 
carbonic  acid  and  ammonia.     When  heated,  it  divides  into 
three  equivalents  of  cyanic  acid,  which  is  thus  obtained  pure. 
The  cyanuric  acid  is  tribasic,  and  forms  three  classes  of 
salts,  in  which  one,  two,  and  three  equivalents  of  its  hydrogen 
are  replaced  by  a  metal. 

883.  The  substance  mentioned  as  a  product  of  the  distilla- 
tion of  sulphocyanate  of  ammonia,  under  the  name  of  melam, 
(880,)  is  a  mixture  of  mellon  with  another  compound,  to 


442  ORGANIC    CHEMISTRY. 

which  the  name  of  melamine  is  given.  This  suhstance  is 
an  amide  of  cyanuric  acid,  and  corresponds  to  the  cyanurate, 
with  three  equivalents  of  ammonia,  which  has  lost  the  elements 
of  six  equivalents  of  water,  C6H3N3O6,:3NH3—  6HO=C6M6N6. 
It  is  obtained  by  dissolving  the  melam  in  a  dilute  solution  of 
potash,  and  crystallizes,  on  cooling,  in  fine  rhombic  octahe- 
drons. Melamine  partakes  of  the  characters  of  an  organic 
base,  and  combines  with  acids,  forming  crystalline  com- 
pounds. When  boiled  with  acids  or  alkalies,  it  takes  the 
elements  of  two  equivalents  of  water,  with  the  evolution  of 
one  of  ammonia,  and  forms  ammeline,  C6H5N5O2,  which  is 
the  amide  of  the  bi-ammoniacal  cyanurate;  the  farther 
action  of  acids  yields  ammelide,  C6H4N4O4 ;  the  amide  of 
the  cyanurate,  with  one  equivalent  of  ammonia.  All  of 
these  bodies  are  decomposed  by  long  continued  ebullition  with 
strong  acids.  They  rcassume  the  elements  of  water,  and 
form  cyanuric  acid  and  ammonia. 

COMPLEX    CYAMDS. 

884.  Several  equivalents   of  the   metallic   cyanids   often 
combine  together  to  form  compounds  in  which  a  portion  of 
the  metals  is  so  united  as  to  be  no  longer  recognised  by  the 
ordinary  tests.     The  cyanid   of  potassium   unites  with   the 
cyanid  of  iron,  and  the  product  has  none  of  the  poisonous 
properties  of  the  simple  cyanid,  nor  is  the  iron  precipitated, 
as  in  the  ordinary  compounds  of  that  metal,  by  potash  and 
alkaline  sulphurets.     These  complex  salts  may  be  considered 
as  derived  from  the  union  of  six  equivalents  of  the  simple 
cyanids.     A  portion  of  the  metal  is  replaced  by  hydrogen 
and  other  metals. 

885.  Ferrocyanids. — A  solution  of  cyanid  of  potassium 
dissolves  metallic  iron  with  the  evolution  of  hydrogen  gas, 
and  the  formation  of  a  cyanid  :  oxyd  of  iron  effects  a  similar 
decomposition,  C2KN  +  FeO  =  KO  +  C2FeN.     Two  equiva- 
lents of  the  resulting  cyanid  of  iron  unite  with  four  of  cyanid 
of  potassium  to  form  the  ferrocyanid  of  potassium,  2C2FeN-f 
4C2KNC12(Fe2K4)N6.    This  is  the  salt  which  has  been  already 
mentioned  under  the  name  of  the  yellow  prussiate  of  potash. 
It  is  prepared  on  a  great  scale  for  the  uses  of  the  arts.     For 
this   purpose  animal   matters,   such   as  dried   blood,   horns, 
leather,  and  other  azotized  substances,  are  calcined  in  close 
vessels  with  carbonate  of  potash.     In  place  of  the  animal 


COMPLEX    CYANID3.  443 

matters  themselves,  the  coal  produced  by  their  calcination  in 
close  vessels,  (animal  charcoal,)  which  contains  nitrogen, 
may  be  employed.  The  alkaline  mass,  which  consists  of 
impure  cyanid  of  potassium,  and  an  excess  of  the  alkaline 
carbonate,  is  digested  with  water,  and  protosulphate  of  iron 
is  added  until  the  precipitate  of  oxyd  of  iron,  at  first  formed, 
no  longer  dissolves  ;  the  liquid  is  then  filtered  and  evaporated, 
when  it  deposits  the  ferrocyanid.  This  salt  forms  large 
tabular  crystals,  which  belong  to  the  trimetric  system,  and 
have  a  fine  lemon-yellow  color ;  they  contain  six  equivalents 
of  water,  which  are  expelled  at  212°.  It  is  very  soluble  in 
water,  but  insoluble  in  alcohol ;  its  taste  is  slightly  saline, 
and  it  is  not  at  all  poisonous,  but  in  large  closes  is  purgative. 
It  is  employed  in  the  arts  for  the  manufacture  of  Prussian 
blue,  and  in  dyeing.  When  fused  with  carbonate  of  potash 
it  is  decomposed,  and  affords  a  mixture  of  cyanate  and  cyanid 
of  potassium  with  metallic  iron.*  Sulphuric  acid  decom- 
poses it  in  part,  with  the  evolution  of  hydrocyanic  acid.f 

*  Upon  this  reaction  M.  Liebig  has  founded  a  very  easy  process 
for  preparing  cyanid  of  potassium.  Eight  parts  of  the  carefully 
dried  ferrocyanid  and  three  parts  of  pure  carbonate  of  potash  are 
intimately  mixed  and  fused  in  a  crucible  (one  of  iron  is  to  be  pre- 
ferred) at  a  bright  red  heat  until  the  evolution  of  gas  ceases,  and  the 
mass  is  in  quiet  fusion.  It  is  then  removed  from  the  fire,  and  after 
standing  a  short  time  to  allow  the  suspended  iron  to  subside,  is 
poured  upon  a  clean  heated  surface  of  stone  or  porcelain.  The 
cooled  mass,  which  should  be  perfectly  white,  is  broken  up  and  pre- 
served in  well  closed  bottles.  The  cyanid  thus  prepared  contains 
about  one-fifth  of  cyanate,  but  is  well  suited  for  all  the  purposes  of 
the  arts,  and  of  chemical  analysis. 

t  A  dilute  acid  is  readily  prepared  by  distilling  a  mixture  of  two 
parts  of  ferrocyanid  of  potassium,  one  of  sulphuric  acid,  and  two 
of  water,  and  collecting  the  product  in  a  receiver  containing  two 
parts  of  water,  until  the  liquid  amounts  to  four  parts.  This  acid, 
from  the  presence  of  a  trace  of  sulphuric  acid,  is  not  liable  to 
decomposition  ;  it  contains  15  or  20  per  cent,  of  pure  acid.  To 
determine  the  amount  of  real  acid  present,  a  weighed  quantity  of 
the  distilled  acid  is  added  to  a  solution  of  nitrate  of  silver,  which 
should  be  in  excess ;  the  precipitate  of  cyanid  of  silver  is  collected 
on  a  filter,  dried  at  212°,  and  weighed.  Its  weight  divided  by  5 
gives  the  amount  of  real  acid  in  the  specimen.  Let  us  suppose  that 
70  grains  of  the  acid  yield  80  of  cyanid  of  silver,  equal  to  16  of  real 
acid,  70  :  16  :  :  100 :  a,  which  equals  22-85 ;  it  then  contains  22-85 
per  cent,  of  real  acid.  But  if  it  is  required  to  reduce  it  to  any 
standard,  as  one  of  3  per  cent.,  which  is  the  ordinary  medicinal  acid, 
then  as  this  will  consist  of  97  of  water  and  3  of  real  acid,  3  :  97  :  : 
16  :  #,  and  x  =  517-3  grains  of  water,  which  must  be  added  to  16  of 


444  ORGANIC    CHEMISTRY. 

886.  When  a  concentrated  solution  of  the  ferrocyanid  is 
mixed    with   strong    hydrochloric   acid,   and    agitated   with 
ether,  a  white  crystalline  substance  separates,  which  must  be 
washed  with  ether,  and  dried  in  vacuo.     This  is  ferrocyanic 
acid  corresponding  to  the  previous  compounds   in  which  the 
potassium  is  replaced  by  hydrogen ;  its  formula  is  C^FcjH.,) 
N6.     It  is  acid  and  astringent  to  the  taste,  and  is   readily 
decomposed   by  exposure   to  the  air.     When  a  solution  of 
ferrocyanid  of  potassium   is  mixed  with   the  salts  of  lime, 
baryta,  and  zinc,  it  forms  white  precipitates  which   have  the 
composition  C12(Fe2KCa3)N6,  &c.     With  salts  of  copper  it 
affords   an   analogous  compound   of  a  deep  reddish   brown 
color;  this  is  a  very  delicate  test   for  that  metal.     The  pre- 
cipitate with  protosalts  of  iron  has  similar  composition  ;  it  is 
of  a  greenish  white,  but  turns  blue   by  exposure  to  the  air. 
With  pcrsalts  of  iron  a  deep  blue  precipitate  is  formed,  which 
is  the  well   known   pigment,  Prussian  blue.     It  contains  C,2 
(Fe2Fc2j  )N6.     In  treating  of  the  sesqui-salts,  (G7G,)  it  was 
shown  that  in  them   two  equivalents  of  iron  replaced  three 
of  hydrogen,  and  consequently  Fej  is  substituted  for  II.     If 
we  represent  Fej  by  Fe#,  the  composition  of  Prussian  blue 
will   be  C^Fe^Fe^N.     To  obtain  the   ferrocyanid  of  iron 
in   a  state  of  purity,  it   is   necessary  that   the   persalt   of 
iron  should  be  in  excess ;  otherwise  the  precipitate  contains 
potassium,    and    is    C^P^KFe^N.       Pure    Prussian    blue 
forms  a  light    porous  mass  of  a    deep  violet    blue,  with    a 
coppery  red   reflection.     It  is  quite  insoluble  in  water  and 
dilute  acids  ;  but  when   recently   precipitated   is  very  soluble 
in  oxalic  acid   and   tartratc  of  ammonia,  forming  deep   blue 
solutions,  which    are   used    as  writing    inks.     When    boiled 
with  a  solution  of  potash,   peroxyd  of  iron  separates,  and 
ferrocyanid  of  potassium  remains  in  solution. 

887.  Ferridcyanid  of  Potassium;  Red  Prussiate  of  Pot- 
ash.— This  salt  is  obtained  when  chlorine  is  passed  through  a 
dilute   solution   of  the    ferrocyanid   of  potassium,  until    the 
solution  no  longer  precipitates  the  persalt  of  iron.     It  is  then 
concentrated  by  evaporation,  and  on  cooling  deposits  crystals 
of  the  new  salt,  which  arc  purified   by  a  second  crystalliza- 

anhydrous  acid  to  reduce  it  to  the  standard.  But  as  70  grains  of 
this  acid  contain  already  51  of  water,  it  is  obvious  that  we  have  to 
add  517-3  —  54  =  463-3  grains  of  water  to  70  grains  of  acid  to  reduce 
it  to  the  required  standard. 


COMPLEX   CYANIDS.  445 

tion.  The  mother  liquor  contains  chloric!  of  potassium, 
C12(Fe2K^)Na  +  Cl:=KCl4-C12(Fe2K3)N6.  If  we  consider  that 
Fe2=Fe^,  it  will  be  seen  that  the  salt  is  referable  to  the  same 
type  as  the  yellow  prussiate,  being  CI2(Fe? K3)N6.  This  beau- 
tiful salt  crystallizes  in  large  prisms  of  a  deep  crimson  red ; 
when  reduced  to  powder  it  is  yellow ;  it  is  readily  soluble  in 
water,  anhydrous,  and  unalterable  in  the  air.  The  solution 
of  this  salt  does  not  affect  the  persalts  of  iron,  but  throws 
down  from  the  solution  of  the  protosalts  a  fine  blue  precipi- 
tate, which  is  CI2(Fe^Fe3)N6.  Its  hue  is  finer  than  that  of 
the  ferrocyanid  of  iron,  and  it  is  known  in  the  arts  as  Turn- 
bull's  blue. 

888.  The  Ferridcyanic  Acid  is  obtained  by  decomposing 
the  ferridcyanid  of  lead  by  dilute  sulphuric  acid.    Its  formula 
is  C12(Fe^H3)N6.     Chromium  and  cobalt  form   compounds 
precisely  similar  in  their  composition  to  the  ferridcyanid. 

889.  Platino-Cyanids.  —  The  platino-cyanid  of  potas- 
sium, C12(Pt3H3)N6,  is  obtained  by  heating  to  low  redness  a 
mixture  of  equal  parts  of  dried  ferrocyanid  of  potassium  and 
spongy  platinum ;  the  mass  is  digested  with  water  and  con- 
centrated by  evaporation,  when  the  salt  is  deposited  in  long 
transparent,   rhomboidal   prisms,  which    are  yellow  by  re- 
flected, and  blue  by  transmitted  light.     The  platino-cyanic 
acid,  C12(Pt3H3)N,  is  obtained  by  decomposing  the  insoluble 
platino-cyanid  of  mercury  by  sulphureted  hydrogen  ;  it  crys- 
tallizes  in   fine   golden-yellow  needles  with  a  coppery  red 
reflection. 

890.  The  other  polymeric  cyanids  have  been  little  studied. 
The  cyanid  of  silver  is  readily  soluble  in  cyanid  of  potas- 
sium, and  the  solution  affords  tabular  crystals  of  a  double 
salt  which  appears  to  correspond  to  the  platino-cyanid,  being 
C,2(Ag3K3)N6.     The  silver  in  this  compound  is  not  preci- 
pitated by  alkaline  chlorids,  but  strong  acids   decompose  it 
with  the  evolution  of  hydrocyanic  acid  and  the  precipitation 
of  cyanid  of  silver.     With  acetate  of  lead  it  gives  a  preci- 
pitate in  which  lead  replaces  the  potassium.    The  two  cyanids 
of  gold  are  soluble  in  cyanid  of  potassium,  and  probably 
form  analogous  compounds. 

891.  These  solutions  are  much  employed  in  electro-gilding ; 
the  precious  metals  being  always  deposited  from  solutions  of 
their   double   cyanids.     These   are   generally   prepared    by 
adding  the  oxyds  to  a  solution  of  cyanid  of  potassium ;  they 

38 


446  ORGANIC    CHEMISTRY. 

are  readily  dissolved,  and  the  double  salts  formed  with  the 
separation  of  potash.* 

FULMINATES. 

892.  The  mutual  action  of  nitric  acid,  alcohol,  and  nitrate 
of  silver  or  mercury,  gives  rise  to  salts  which  are  distinguished 
by  exploding  violently  by  heat  or  percussion,  and  have  hence 
been  described  under  the  name  of  fulminates. 

The  Fulminate  of  Mercury  (C4Hg2N2O4)  is  prepared  by 
the  following  process  :  One  ounce  of  mercury  is  dissolved,  by 
a  gentle  heat,  in  an  ounce  and  a  half,  by  measure,  of  nitric 
acid,  specific  gravity  1-4,  and  the  solution  poured  into  ten 
measured  ounces  of  alcohol,  specific  gravity  '830.  A  violent 
action  immediately  takes  place,  after  a  few  minutes,  with  the 
evolution  of  copious  white  fumes ;  after  this  is  over  the  ful- 
minate is  formed  in  white  crystalline  grains ;  it  is  to  be  care- 
fully washed  with  cold  water,  and  dried  by  a  gentle  heat. 
It  is  slightly  soluble  in  boiling  water,  and  crystallizes,  on 
cooling,  in  feathery  crystals.  It  explodes  violently  by  a  heat 
of  390°,  by  the  contact  of  concentrated  sulphuric  and  nitric 
acids,  or  by  percussion,  and  is  employed  in  the  preparation 
of  the  percussion  caps  for  fire-arms. 

893.  The  Fulminate  of  Silver  (C4Ag2N2O4)  is  prepared 
by  a  similar  process.     It  is  much  more  dangerous  than  the 
last ;  the  slightest  friction  between  two  hard  surfaces,  even 
under  water,  will  cause  it  to  explode  with  fearful  violence. 
It  is  very  poisonous. 

The  true  nature  of  these  compounds  is  not  known ;  they 
have  been  regarded  as  the  salts  of  a  bibasic  acid,  C4H2N2O4. 
which  is  polymeric  of  cyanic  acid;  but  this  acid  is  unknown. 
One  equivalent  of  the  metal  is  combined,  as  in  the  complex 
cyanids,  in  such  a  manner  that  it  cannot  be  separated  by  the 
ordinary  reagents ;  the  other  equivalent  is  capable  of  being 
replaced.  When  the  silver  salt  is  dissolved  in  acid,  one-half 
of  its  silver  separates,  and  an  acid  salt  crystallizes  on 
cooling,  which  is  C4AgHN2O4;  potash  or  baryta,  in  the  same 
way,  precipitate  one  equivalent  of  silver,  and  form  salts  of 
the  formula  C4AgKN2O4.  M.  Gahardt  regards  them  as 
nitric  species  of  a  genus  which  is  the  homologue  of  the 

*  For  this  classification  of  the  cyanids,  as  well  as  for  many  other 
important  aids,  this  portion  of  the  work  is  indebted  to  M.  Gahardt's 
excellent  Precis  de  Chimie  organique. 


ALCARSINE,  AND    THE   BODIES   DERIVED    FROM   IT.        44-7 

cyanids,  and  will  be  C4H3N.  The  nitric  species,  in  which 
Ihe  residue  of  nitric  acid  (675)  NHO6 — O2  replaces  H2,  will 
be  C4H(NH04)N=C4H2N204.  The  reasons  for  this  are  the 
resemblance  of  the  fulminates  to  the  complex  cyanids,  and 
the  results  of  their  decomposition  by  sulphureted  hydrogen, 
which  is  analogous  to  that  of  other  nitric  compounds. 


ALCAESINE,  AND    THE    BODIES    DERIVED    FROM    IT. 

894.  When  a  mixture  of  equal  parts  of  arsenious  acid  and 
acetate  of  potash  is   distilled  at  a  long  red   heat,  there  is 
obtained,  among  other  products,  a  volatile  liquid   to  which 
the  name  of  alcarsine   is   given.     When    purified   it   is  a 
colorless  liquid,   slightly  soluble  in   water,  and   of  specific 
gravity   1-462 ;    it    boils   at    300°,   and   distils   unchanged. 
Its    odor    is    very    disagreeable,     resembling    arseniureted 
hydrogen ;  applied  to  the  skin  it  is  corrosive,  and  taken  in- 
ternally it  is  an  energetic  poison.     Exposed  to  the  air  it 
takes  fire  and  burns  with  a  white  flame,  evolving  vapors  of 
arsenious  acid.     The  formula  of  alcarsine  is  C8H12As2O2 ; 
four  equivalents  of  acetic  and  two  of  arsenious  acid  contain 
the  elements  of  eight  equivalents  of  carbonic  acid,  four  of 
water,  and  one  of  alcarsine ;  carbonate  of  potash   remains. 
Alcarsine  combines   directly  with  acids,  forming  crystalline 
compounds ;  it  is  a  true  alkaloid,  in  which  arsenic  replaces 
nitrogen.     The  oxygen    in  this  substance  may  be  replaced 
by  sulphur  and  selenium,  forming  compounds  which  resemble 
the  normal  alcarsine. 

895.  When  alcarsine  is  distilled  with  concentrated  hydro- 
chloric acid  or  chlorid  of  mercury,  a  colorless    liquid    is 
obtained,  which  is  called  chlorarsine.     One  equivalent  of 
alcarsine  and  two  of  hydrochloric  acid   yield  two  of  water 
and  two  of  chlorarsine,  C8H12O2As2-f-2HCl=2HO  +  2C4H5 
AsCl.      It  has  a  most   disgusting   odor,  and   its  vapor   is 
spontaneously  inflammable.     Similar  compounds  are  obtained 
with    hydrobromic   and    hydriodic   acids.      Chlorarsine    is 
decomposed    by    salts   of    silver,    which   precipitate   all   its 
chlorine ;  this  element  appears  to  exist  in  it  as  hydrochloric 
acid.     These  compounds  may  be  regarded  as  the  salts  of  an 
alkaloid,  arsine,  which  is  C4H5As,  and   the   hydrochlorate 
will  be  C4H5As,HCl.     The  arsine  has  not  yet  been  isolated, 
but  the  compounds  above  described  are  precisely  similar  to 
the  salts  of  the  alkaloids. 


448  ORGANIC    CHEMISTRY. 

896.  When  chlorarsine  is  digested  with   zinc  or  iron,  at  a 
temperature  of  212°,  a  metallic  .chlorid   is   formed  without 
any  evolution  of  gas,  and   a   liquid   remains,  to  which  M. 
Bunsen,  its  discoverer,  has   given  the  name  of  kakodyle* 
He  assigns  to  it  the   formula,  C4H6As,  and   regards  it  as  the 
radical  of  the  previous  compounds,  and  as  combining  directly 
with  oxygen  and  chlorine  like  a  metal ;  but  its  real  formula 
is  CsH,2As2,  and  it  cannot  consequently  exist  in  chlorarsine, 
whose  equivalent,  as   deduced  from  its   compounds  and  the 
specific  gravity  of  its  vapor,  is    represented  by  C4H5As,HCl. 
Its  relations  to  these  compounds   is   analogous  to  that  which 
exists 'between   cyanogen   and   the  cyanids.     Kakodyle  is  a 
colorless  liquid,  of  a  most  disagreeable  odor,  and  is  fearfully 
poisonous  ;  it  fumes   and  takes   fire  on   exposure  to  the  air, 
but  if  covered  by  water,  is  slowly  oxydized  and  yields  alcar- 
sine. 

897.  When  kakodyle  and  alcarsine   are   gradually  oxy- 
dized  at   a    low   temperature,    a     crystalline   compound    is 
obtained,  which  is  called  alcargene.     It  is   best  obtained  by 
bringing  alcarsine  in  contact  with  oxyd  of  mercury  under 
water ;  metallic  mercury  separates,  and  pure  alcargene  remains 
in  solution.     Its  composition  is  C4H5As04 ;  one  equivalent  of 
alcarsine  and  eight  of  oxygen  yield   two  of  water,  and  two 
of  the  new  compound,  C8H,aAs2O2  +  8O— 2HO  +  2C4H5AsO4. 
This  body  forms   large  transparent  rhombic  prisms,  readily 
soluble  in  water,  and  less  so  in  alcohol.     It  is  inodorous,  has 
a  feeble  taste,  and  is  not  at  all  poisonous,  even  in  large  doses. 
It  may  be  boiled  with  nitric  acid  without  change,  but  deoxy- 
dizing  agents  convert  it  into  alcarsine.     Alcargene  combines 
with  acids  and  salts,  like  an  alkaloid,  while,  at  the  same  time, 
it  acts  as  an  acid,  and  decomposes   the   alkaline  carbonates, 
forming  monobasic  salts.     By  the  action  of  dry  sulphureted 
hydrogen,  a  compound   is  obtained,  in  which  the  oxygen  is 
replaced  by  sulphur.     It  forms  large  colorless  crystals  of  an 
alliaceous  odor,  having  the  formula  C4H5AsS4. 

URIC    ACID,    AND    THE    PRODUCTS    OF    ITS    DECOMPOSITION. 

898.  This  substance  is  found  in  the  urinary  secretion  of 
nearly  all  animals  ;  the  solid  urine  of  serpents,  birds,  and 

*  From  the  Greek  JcaJcos^  evil,  and  hule,  principle,  in  allusion  to  its 
noxious  properties. 


URIC  ACID,  AND  THE  PRODUCTS  OF  ITS  DECOMPOSITION.  449 

insects,  is  almost  entirely  urate  of  ammonia.  To  prepare  it, 
the  urine  of  the  boa  constrictor,  or  other  serpents,  is  boiled 
with  a  solution  of  caustic  potash,  until  the  evolution  of  am- 
monia ceases.  A  current  of  carbonic  acid  gas  is  then  passed 
through  the  liquid,  which  precipitates  urate  of  potash,  while 
the  impurities  are  held  in  solution.  This  precipitate  is  washed 
with  cold  water,  in  which  it  is  sparingly  soluble,  and  dis- 
solved in  a  dilute  solution  of  potash  ;  from  this  solution, 
hydrochloric  acid  precipitates  uric  acid  in  a  gelatinous  mass, 
which  by  a  gentle  heat  changes  into  a  crystalline  precipitate. 
It  is  a  white  crystalline  powder,  which  is  almost  insoluble  in 
water;  it  is  bibasic,  and  its  formula  is  Ci0H4N4O6.  The 
urates  are  very  sparingly  soluble  salts. 

899.  By  the  action  of  oxydizing  agents,  uric  acid  yields 
many  interesting   products.     Boiled  with   peroxyd  of  lead, 
carbonic  acid  gas  is  evolved,  and  the  liquid  contains  a  crys- 
talline compound  called  allantoine,  which  exists  in  the  am- 
niotic  fluid  of  the  cow.     Its  composition  is  C8H6N4OG.     The 
reaction  is  thus  expressed  :    C10O4N4O6  +  2HO  -f  2PbO2  — 
2C02  +  C8H6N4O6-f  2PbO.     The  farther  action   of  peroxyd 
of  lead  converts  allantoine  into  urea  and   oxalate  of  lead, 
C8HCN4O6  -f  2HO  +  2PbO2  equals  two  equivalents  of  urea, 
2C2H4N2O2,  and  one  of  oxalate  of  lead,  C4Pb2O8. 

When  uric  acid  is  gradually  added  to  four  times  its  weight 
of  nitric  acid,  specific  gravity  1*425,  it  dissolves  with  the  evo- 
lution of  carbonic  acid  and  nitrous  vapors,  and,  on  cooling, 
deposits  alloxan,  which,  by  a  second  crystallization,  is  obtained 
in  large  colorless  prisms  very  soluble  in  water ;  the  mother 
liquor  contains  ammonia.  Its  formula  is  C8H4N2OI0.  One 
equivalent  of  uric  acid  with  six  of  water,  and  two  equivalents 
of  oxygen  from  the  nitric  acid,  yield  two  equivalents  of  car- 
bonic acid,  two  of  ammonia,  and  one  of  alloxan.  Ci0H4N4O6  -f 
6HO  +  2O=2CO2  +  2NH3  +  C8H4N2O10.  If  the  nitric  acid  is 
either  more  concentrated  or  more  dilute,  or  if  heat  is  applied, 
the  nitrous  acid  formed  reacts  upon  the  ammonia,  and  from 
their  mutual  decomposition  nitrogen  gas  is  evolved.  The 
farther  oxydation  of  alloxan  transforms  it  into  carbonic  gas, 
oxalic  acid,  and  urea,  and  hence  these  latter  substances  are 
found  as  secondary  products  of  the  action  of  nitric  upon  uric 
acid. 

900.  By  the  action  of  deoxydizing  agents  alloxan  is  con- 
verted  into  alloxantine ;   if  a  solution  of  it  is  mixed  with 
hydrochloric  acid  and  placed  in  contact  with  a  slip  of  zinc, 

38* 


450  ORGANIC    CHEMISTRY. 

it  deposits  crystals  of  alloxantine;  the  same  change  is 
effected  by  the  action  of  sulphureted  hydrogen  gas.  Allox- 
antine is  also  obtained  when  an  excess  of  uric  acid  is  added 
to  dilute  boiling  nitric  acid ;  its  formula  is  C^H^N^^,  and  it 
is  derived  from  the  elements  of  two  equivalents  of  alloxan  by 
the  addition  of  two  of  hydrogen,  2C8H4NA0  +  2II=C,6H,0 
N4Oi0.  Alloxantine  bears  the  same  relation  to  alloxan  as 
indigogene  does  to  indigo.  It  forms  colorless  prisms  very 
sparingly  soluble  in  cold  water ;  when  boiled  with  dilute 
nitric  acid  it  is  converted  into  alloxan.  When  its  solution  is 
mixed  with  a  solution  of  sal  ammoniac,  crystals  of  uramile 
(C8H5N3O6)  are  deposited,  and  the  liquid  contains  alloxan  and 
free  hydrochloric  acid,  C16H10N4O?04-HCl,NH3=C8H5iN3O6-f 
HCl  +  C8H4N2O10-f  4HO.  Uramile  is  the  amide  of  dialuric 
acid,  (C8H4N2Og,)  and  when  boiled  with  alkalies  or  acids 
takes  up  the  elements  of  water  and  is  converted  into  am- 
monia and  this  acid,  which  is  also  obtained  by  the  prolonged 
action  of  sulphureted  hydrogen  upon  a  solution  of  alloxantine. 

901.  When  carbonate  of  ammonia  is  added  drop  by  drop 
to  a  solution  of  alloxan   maintained   nearly  at  the  boiling- 
point,  carbonic  acid   is  disengaged  and  the  liquor  becomes 
purple ;  the  addition  is  continued  until  the  liquid  has  a  feeble 
odor  of  ammonia,  and  it  is  then  set  aside  to  cool,  when  it 
deposits   crystals   of  murexide.      This    beautiful    substance 
forms  square  prisms,  which  have  a  magnificent  golden-green 
color  like  the  wing-cases  of  the  golden   beetle;   by  trans- 
mitted   light  they  are   garnet-red.     Murexide    is   sparingly 
soluble  in  water ;  its  formula  is  C,6H8NgO8,  and  it  is  formed 
from  two  equivalents  of  alloxan  and  four  of  ammonia  by  the 
separation  of  twelve  of  water,  2C8H4N2O,0  +  4NH3=:CWjH8Ns 
O8-{-  12HO.    Murexide  is  produced  in  several  other  reactions  ; 
when  a  solution  of  uramide,  with  a  little  ammonia,  is  boiled 
with  oxyd  of  silver,  crystals  of  it  are  deposited  while  the 
metal    is    reduced.     The   same   solution   gradually  absorbs 
oxygen  from  the  air,  and  undergoes  the  same  change ;  two 
equivalents  of  uramile,  with  two  of  ammonia  and   four  of 
oxygen,  yield  one  of  murexide  and  eight  of  water,  2CSH5N3 
OG  +  2NH3-fO4=C16H?NA  +  8HO.     The   solution  of  uric 
acid  in  strong  nitric  acid  may  be  employed  in  place  of  alloxan 
for  the  preparation  of  this  substance. 

902.  When  uric  acid  or  alloxan  is  boiled  for  some  time 
with  an  excess  of  strong  nitric  acid,  it  evolves  carbonic  acid, 
and  deposits  on  evaporation  and  cooling  crystals  of  para- 


HIPFURIC    ACID.  451 

banic  acid,  C6H2N2O6.  This  substance  is  very  soluble,  and 
has  a  well  marked  acid  reaction ;  when  its  solution  is  neu- 
tralized by  ammonia  and  boiled,  it  combines  with  the 
elements  of  two  equivalents  of  water,  and  is  converted  into 
oxalur ate  of  ammonia.  The  oxaluric  acid  is  C6H4N2O8; 
when  its  solution  is  boiled  it  takes  the  elements  of  two 
equivalents  of  water,  and  is  resolved  into  oxalic  acid  and 
urea,  C6H4NA+ 2HO=C4H2O8+ C2H4N2O2. 

Uric  acid  yields  many  other  products  of  interest,  which 
are  described  in  the  larger  works ;  the  study  of  these 
reactions  is  very  instructive,  as  it  shows  us  the  effects  of 
different  reagents,  and  the  laws  which  regulate  the  trans- 
formations of  substances. 

HIPPURIC    ACID. 

903.  This  substance  exists  in  human  urine,  or  in  still 
larger  quantities  in  that  of  cows  and  horses.  From  the 
latter  it  may  be  prepared  by  mixing  the  fresh  urine  with 
milk  of  lime  until  it  acquires  an  alkaline  reaction.  The 
precipitate  formed  is  allowed  to  subside,  and  the  clean  liquid 
rapidly  evaporated  to  about  one-tenth.  It  is  then  mixed  with 
a  slight  excess  of  hydrochloric  acid,  which  on  cooling  sepa- 
rates impure  hippuric  acid.  This  is  purified  by  solution  in  hot 
water,  and  digesting  with  a  little  animal  charcoal ;  the 
filtered  solution  deposits  pure  hippuric  acid  on  cooling.  It 
forms  large  white  prisms,  and  is  readily  soluble  in  hot  water, 
but  requiring  400  parts  of  cold  water  for  solution.*  Its 
formula  is  C18H9NO6.  When  hippuric  acid  is  boiled  with 
peroxyd  of  lead  it  evolves  carbonic  acid,  and  the  solution 
contains  benzamide,  Cj8H9NO6  -j-  O6  =  C14H7NO2  +  4CO2  + 
2HO.  If  a  solution  of  hippuric  is  boiled  for  half  an  hour 
with  a  strong  acid,  as  the  hydrochloric,  it  deposits  on  cooling 
a  large  quantity  of  benzoic  acid,  and  the  liquid  by  evaporation 
affords  crystals,  which  are  a  compound  of  hydrochloric  acid, 


*  A  curious  instance  of  the  formation  of  hippuric  acid  is  observed 
when  benzoic  acid  is  taken  into  the  stomach  ;  an  adult  can  swallow 
half  an  ounce  of  it  without  any  unpleasant  effects,  and  in  the  course 
of  eight  or  ten  hours  the  excreted  urine  will  contain  an  amount  of 
hippuric  acid  equivalent  to  that  of  the  benzoic  acid  taken,  while  the 
normal  urine  contains  but  a  very  small  portion  of  it.  It  is  hence 
inferred  that  the  hippuric  is  formed  from  the  benzoic  acid  by 
the  action  of  the  organism,  but  no  process  is  known  by  which  it  can 
be  produced  artificially. 


452  ORGANIC    CHEMISTRY. 

with  a  peculiar  sweet  substance  which  was  originally 
obtained  by  the  decomposition  of  gelatine,  and  hence  named 
glycocoll*  or  sugar  of  gelatine,  CJ^NOe  +  SHC^CuHeC^ 
+  C4H5N04. 

904.  Glycocoll  has  a  taste  resembling  that  of  grape  sugar  ; 
it  is  nearly  insoluble  in   alcohol,  but  soluble  in   four  or  five 
parts  of  water,  and  crystallizes   readily  from  its  solutions. 
It  combines  directly  with  the  acids  to  form  beautifully  crystal- 
lized compounds,  in  which  it  appears  to  act  the  part  of  an 
organic  base.     At  the  same  time  it  dissolves  metallic  oxyds, 
and  forms  compounds,  in  which  an  equivalent  of  its  hydrogen 
is  replaced  by  a  metal. 

Glycocoll  is  closely  related  to  alcargene,  which  may  be 
regarded  as  glycocoll  in  which  arsenic  takes  the  place  of 
nitrogen  ;  these  two  substances  also  resemble  each  other  in 
performing  the  double  function  of  bases  and  acids,  and  in 
their  general  physical  characters. 

NUTRITIVE    SUBSTANCES    CONTAINING    NITROGEN. 

905.  All  vegetables   afford,  in   addition   to  lignine,  starch, 
sugar,  and  the  other  bodies  before  described,  a  peculiar  class 
of  compounds  which  contain  nitrogen  and  a  small  quantity 
of  sulphur.     These  substances  are  tasteless,  often  insoluble 
in  water,  and  are   highly  nutritious.     They  occur  to  a   still 
greater  extent  in  animals,  of  which  they  constitute  the  mus- 
cular fibre,  and    are    dissolved    in    the    fluids    of  the  body. 
These  substances  arc  very  analogous  in   their  composition 
and  chemical  characters. 

906.  Vegetable  albumen  is  found  in   the  juices  of  many 
plants.     It  closely  resembles  animal  albumen,  and  like  it  is 
coagulated  by  heat.     When  a  paste  of  wheat  flour  is  washed 
with  water,  a  large  quantity  of  starch  separates,  and  a  very 
tenacious    substance    remains,  which    is   known   as  gluten, 
and  is  principally  vegetable  fbrinc.     It  forms  a  gray  trans- 
lucent mass  which  is  soluble  in  acetic  acid.     Legumine,  or 
vegetable  caseine,  is  found  in  the  seeds  of  beans  and  peas. 
When  the   seeds  are  bruised  with  water,  the  legumine  dis- 
solves ;  acetic  acid  coagulates  the  solution,  and  precipitates 
it  in  a  form  resembling  the  curd  of  milk. 

907.  These  substances  are  very  prone  to  decomposition, 

*  From  the  Greek  glukus,  sweet,  and  kolla,  glue. 


NUTRITIVE    SUBSTANCES    CONTAINING    NITROGEN.        453 

and  when  exposed  to  air  and  moisture,  soon  undergo  putre- 
faction. The  remarkable  power  which  they  possess  to  in- 
duce change  in  other  bodies  has  been  frequently  noticed.  The 
conversion  of  sugar  into  lactic  and  butyric  acids,  is  due  to  the 
action  of  decomposing  caseine,  (772,)  and  synaptase,  (856,) 
which  is  an  analogous  compound,  probably  owes  its  singular 
power  of  decomposing  amygdaline  and  emulsine  to  a  similar 
condition.  Diastase  (780,)  is  a  modified  form  of  gluten. 
Yeast,  (770,)  which  is  a  deposit  from  beer  and  other  fermenting 
liquids,  is  similar  to  these,  and  identical  with  the  substance  men- 
tioned as  producing  the  vinous  fermentation.  The  process  of 
bread-making  illustrates  the  action  of  this  substance.  The 
essential  ingredients  in  flour  are  vegetable  fibrine,  starch,  and 
sugar.  The  flour  is  made  into  a  paste  with  water,  yeast  is 
added,  and  the  mixture  is  put  iji  a  warm  place.  The  yeast 
induces  the  vinous  fermentation  in  the  sugar,  forming  alcohol 
and  carbonic  acid  gas,  which,  from  the  viscid  nature  of  the 
paste,  inflates  it,  and  gives  to  it  its  peculiar  lightness  and 
porosity.  The  power  of  yeast  and  similar  bodies  is  com- 
pletely destroyed  by  boiling  water,  strong  alcohol,  essential 
oils,  various  metallic  salts,  and  many  other  substances,  all  of 
which  are  known  to  act  as  antiseptics. 

908.  Animal  Albumen. — This   substance  is  found  abun- 
dantly in  the  white  of  eggs  and  the  serum  of  the  blood.     Al- 
bumen  is  soluble  in  water,  especially  with  the   aid   of  an 
alkali,  but  is  readily  precipitated  from  its  solutions  by  acids. 
When  exposed  to  a  temperature  of  about  150°,  it  is  changed 
into  a  white  mass  which  is  no  longer  soluble. 

Animal  Fibrine.  —  This  substance  is  dissolved  in  the 
chyle  and  blood,  and  constitutes  the  muscular  parts  of  animals. 
It  is  easily  obtained  by  stirring  freshly  drawn  bullock's 
blood  ;  the  fibrine  adheres  to  the  stick  and  may  afterwards 
be  washed  with  water.  It  is  a  white  fibrous  mass,  which 
when  dry  is  horny  and  translucent.  Fibrine  is  readily  solu- 
ble by  a  gentle  heat  in  solutions  of  sal  ammoniac,  nitre,  and 
several  other  salts.  When  thus  dissolved,  it  has  the  proper- 
ties of  soluble  albumen  and  is  coagulated  by  heat.  Both 
fibrine  and  coagulated  albumen  are  soluble  in  water,  contain- 
ing 2~^o"otn  Part  °f  hydrochloric  acid. 

909.  Caseine. — This   substance   constitutes   the  curd  of 
milk.     When  pure  it  is  quite  insoluble  in  water ;  but  in  milk 
it  is  rendered  soluble  by  combination  with  a  little  alkali.     Its 
solution  is   immediately  coagulated   by  dilute  acids,  which 


454  ORGANIC    CHEMISTRY. 

combine  with  the  precipitated  caseine.  The  spontaneous 
coagulation  of  milk  is  due  to  the  formation  of  lactic  acid 
from  the  sugar  of  milk,  by  the  agency  of  a  portion  of  the 
caseine  in  a  state  of  insipient  decomposition,  (772.)  This 
change  goes  on  until  the  whole  of  the  sugar  is  converted  into 
lactic  acid.  In  the  manufacture  of  cheese,  the  process  is 
facilitated  by  the  addition  of  a  little  rennet.  This  substance 
is  prepared  by  digesting  the  lining  membrane  of  a  calf's 
stomach  in  water,  and  appears  to  act  like  caseine  by  impart- 
ing to  the  milk  its  peculiar  condition. 

910.  Proteine. — When  any  one  of  these  bodies  is  dis- 
solved in  a  dilute  solution  of  potash  by  a  gentle  heat,  acetic 
acid  precipitates  from  the  liquid  a  white  pulverulent  substance, 
which  Mulder,  its   discoverer,  has  named  proteine.*     The 
composition  of  this  body  is  the  same,  from  whatever  source 
it  is  obtained,  and  leads  to  the  formula  C^HaoNjO^.     The 
substances  from  which  it  is  derived  always  contain  phosphate 
of  lime,  and  frequently  salts  of  soda.     Beside  this,  there  is 
invariably  present  a  small  portion  of  sulphur,  and  in  albumen 
and  fibrine,  traces  of  phosphorus.     The  quantity  of  sulphur 
is  small,  being  on  an  average  about  -j^-th  part ;  it  is  sepa- 
rated in  the  form  of  sulphuret  of  potassium  when  the  sub- 
stance is  dissolved  in  potash,  and  can  be  detected  by  a  salt  of 
lead,  which  affords  with  the  solution  a  black  precipitate  of 
sulphuret  of  lead.     The  proportions  of  oxygen,  hydrogen, 
nitrogen,  and  carbon,  in  these  bodies  are  the  same  as  those  in 
proteine. 

911.  We  may  conceive  proteine  to  be  allied  to  fibrine, 
albumen,  &c.,  in  the  same  manner  as  dextrine  is  to  starch 
and  cellulose.     The  different  condition  of  these  several  sub- 
stances may  be  regarded  as  the  result  of  organization,  for 
we  have  seen  that  fibrine   may  be  readily  converted   into 
albumen  without  any  change  of  composition.     The  sulphur 
in  these  compounds  is  probably  due  to  the  presence  of  a  sul- 
phureted  body  not  yet  separated,  which  is  decomposed  by  the 
potash.     As  its  quantity  is  very  small  and  the  proportions  of 
its  organic  elements  quite  similar  to  those  of  proteine,  we 
observe  no  difference  between  the  analyses  of  proteine  and 
the  organic  tissues. 

912.  Proteine  and  all  the  bodies  of  this  class  are  soluble 


*  From  the  Greek,  proteuo,  I  take  the  pre-eminence,  in  allusion  to 
the  large  class  of  substances  of  which  it  is  supposed  to  be  the  basis. 


THE  BLOOD.  455 

in  strong  hot  hydrochloric  acid,  and  yield  a  purple  solution* 
which,  by  exposure  to  the  air,  absorbs  oxygen  and  becomes 
black.  It  then  contains  sal  ammoniac  and  a  substance  identical 
with  the  humic  acid  noticed  before  (785)  as  a  result  of  the 
decay  of  woody  fibre ;  its  composition  may  be  expressed  by 
the  formula  C40H12O12.  The  elements  of  one  equivalent  of 
proteine  and  three  of  oxygen  yield  humic  acid  with  five  equi- 
valents of  ammonia,  which  unite  with  the  hydrochloric  acid 
and  three  of  water,  C^Ha^O^-i-  3O=C40H12O12+5NH3  + 
3HO. 

913.  Gelatine. — This  substance  is  obtained  from  many 
animal  tissues,  as  the  skin,  cellular  membranes,  tendons,  and 
ligaments,  and  also  from  the  bones,  which  contain  about  forty 
per  cent,  of  soluble  matters.     It  is  extracted  from  these  sub- 
stances by  boiling  with  water,  and  the  solution  on  cooling 
becomes  a  firm  jelly ;  this  property  is  very  characteristic  of 
gelatine.     It  is  found  nearly  pure  in  isinglass  or  fish  glue. 
This  substance  does  not  exist  in  the  tissues  in  a  soluble  form, 
but  in  a  condition  which  is  probably  related  to  the  soluble 
gelatine  as  starch  is  to  dextrine,  (779.)     It  is  in  fact  a  pro- 
duct of  the  action  of  boiling  water  upon  the  insoluble  gelatine. 
Its  solution  forms  a  very  insoluble  precipitate  with  an  infusion 
of  nut-galls,  or  a  solution  of  tannic  acid.    When  the  skin  of 
animals  is  steeped  in  an  infusion  of  oak  bark  or  of  any  other 
vegetable  containing  tannic  acid,  this  insoluble  compound  is 
formed  and  constitutes  leather.     The  formula  of  gelatine  is 
C13Hi0N2O5.     The  substance   of  cartilage  has  been  named 
chondrine  ;  it  resembles  gelatine  in  its  properties,  but  differs 
a  little  in  composition ;  both  of  these  bodies,  like  the  proteine 
compounds,  contain  traces  of  sulphur. 

914.  If  one  part  of  gelatine  is  mixed  with  two  of  concen- 
trated sulphuric  acid,  it  dissolves  in  a  few  hours,  and  forms 
a  viscid  liquid ;  this  is  diluted  with  nine  parts  of  water,  and 
boiled  for  six  or  eight  hours ;  the  acid  is  then  neutralized  by 
chalk,  and  the  clear  liquid  evaporated  to  a  syrup,  which 
gradually  deposits  transparent  crystals  of  glycocoll  or  sugar 
of  gelatine,  (903.) 

THE    BLOOD. 

915.  This  substance,  when  recently  taken  from  the  body, 
is  a  homogeneous  slightly  viscid  liquid,  but  soon  forms  a 
tremulous  jelly,  which   by   standing  contracts  into  a  hard 
coagulum,  floating  in  a  yellowish  liquid  called  the  serum. 


456  ORGANIC    CHEMISTRY. 

This  has  a  saline  taste,  and  contains  in  solution  alkaline 
chlorids  and  phosphates,  with  a  large  portion  of  albumen. 
It  has  an  alkaline  reaction,  which  is  due  to  the  presence  of 
the  tribasic  phosphate  of  soda. 

The  coagulum  of  the  blood  has  a  dark-red  color,  and 
consists  of  a  mass  of  fibrine  mixed  with  the  red  globules, 
which  constitute  the  coloring  matter  of  the  blood.  If  the 
fresh  liquid  is  mixed  with  several  volumes  of  a  solution  of 
sulphate  of  soda,  the  fibrine  remains  dissolved,  (908,)  and 
the  globules  collect  at  the  bottom  of  the  liquid  as  a  sediment. 

910.  The  form  and  size  of  these  globules  vary  in  different 
animals ;  in  the  blood  of  man  they  arc  thin  discs  from  -j^Vff 
to  s-ffVff  °f  an  *nch  m  diameter.  They  consist  of  a  colorless 
sac,  of  a  composition  similar  to  fibrine,  which  encloses  a 
soluble  red  matter.  When  placed  in  water,  these  corpuscles 
burst  and  form  a  red  liquid  containing  albumen  and  the 
coloring  principle,  which  is  named  hematinc.  This  is 
readily  soluble  in  alcohol  containing  a  little  acid  or  ammonia, 
by  which  it  is  separated  from  the  albumen.  The  solution 
has  a  deep  red  color  even  when  much  diluted.  Pure 
hematinc  contains  about  6  per  cent,  of  iron,  which  cannot  be 
separated  from  it  by  dilute  acids.  Its  composition  may  be 
expressed  by  the  formula  C^H^^OgFe.  If  it  is  mixed  with 
strong  sulphuric  acid,  and  water  gradually  added  to  the 
mixture,  hydrogen  gas  is  evolved,  and  the  hematine  separates 
as  a  dark-rcxi  mass,  while  the  iron  remains  in  solution. 
The  hematinc  thus  prepared  is  entirely  free  from  iron ;  but 
its  composition  is  in  other  respects  the  same  as  before,  being 
CuII^NaOg.  This  shows  that  the  red  color  of  the  blood  is 
not  necessarily  due  to  the  compounds  of  iron,  as  has  been 
supposed,  and  that  the  iron  docs  not  exist  in  the  blood  as  an 
oxycl. 

917.  The  color  of  the  arterial  blood  is  scarlet,  while  that 
in  the  veins  is  a  dark-red,  and  the  solutions  of  hematine  have 
the  same  tint.  The  venous  blood  acquires  the  bright  scarlet 
tint  while  in  the  lungs,  but  loses  it  again  in  the  capillary 
vessels.  This  change  has  been  attributed  to  the  absorption 
of  oxygen  by  the  coloring  matter,  but  hematine  undergoes 
no  change  of  color  by  the  action  of  the  air.  If  we  mix 
arterial  blood  with  water,  it  immediately  assumes  a  dark-red 
color,  which  is  not  altered  by  oxygen  gas  ;  but  a  solution 
of  any  neutral  salt  will  restore  the  scarlet  tint,  even  in  a 
vacuum.  A  little  milk,  or  a  mixture  of  chalk  and  water, 


THE    GASTRIC    JUICE.  457 

will  immediately  give  a  bright  color  to  venous  blood  or  a 
solution  of  hematine.  This  effect  seems  due  to  the  light 
reflected  from  the  white  particles,  and  the  saline  liquids 
produce  the  same  effect  by  coagulating  the  exterior  of  the 
globules  and  rendering  them  white.  Mulder  supposes  that 
the  action  in  the  lungs  consists  in  an  oxydation  of  a  portion 
of  the  fibrine  of  the  blood,  by  which  a  white  layer  of  oxyd 
of  proteine  is  formed  on  the  surface  of  the  blood  globules. 
This  oxyd  is  taken  up  in  the  capillary  vessels,  and  the 
globules  reacquire  their  dark-red  tint.  This  view  must  be 
considered  as  only  an  ingenious  hypothesis,  but  it  is  certain 
that  the  difference  of  color  is  not  due  to  any  change  in  the 
hematine  itself. 

918.  In  addition  to  the  substances  already  mentioned,  the 
blood  contains  globules  of  fatty  matter.     1000  parts  of  blood 
afford  790   parts  of  water,  68  of  albumen,  and   10-9  parts 
of  salts  with  a  little  fat,  which  are  dissolved  in  the  serum. 
The  clot  contains  about  138-6  parts  of  albumen  and  fibrine, 
and  2-97  parts  of  hematine,  besides  2-4  parts  of  fatty  sub- 
stances which  contain  phosphorus.     The  salts  of  the  blood 
are    principally    alkaline    chlorids    and    phosphates,    with 
phosphate  of  lime.     The  proportions  of  the  ingredients  often 
differ  from  these,  being  varied  by  many  circumstances. 

919.  Chyle. — This  fluid  is  taken  up  by  the  lacteals  from 
the  smaller  intestines,  as  a  white  opake  fluid.     It  contains 
a   proteine  compound   in   solution,  and  a  great  number  of 
globules  of  fat  to  which  its  milky  appearance  is  due,  besides 
various  salts,  and  a  small  portion  of  iron  in  a  soluble  form. 
When  the  chyle  is  first  taken  up  by  the  lacteals,  it  contains  but 
little  fibrine,  but  a  large  portion  of  albumen.     But  the  chyle 
from  the  thoracic  duct  coagulates  like  the  blood  into  clots 
which  contain   fibrine,  while  the  clear   fluid  that  separates 
resembles  the  serum  of  the  blood.     LympJi,  the  fluid  of  the 
lymphatic  vessels,  differs   from  chyle  principally  in  being 
more  dilute,  and  in  the  absence  of  the  fatty  globules. 


THE    GASTRIC    JUICE. 

920.  This  fluid  is  secreted  from  the  coats  of  the  stomach 
by  the  stimulus  of  food.  It  is  a  slightly  saline  fluid  with  an 
acid  reaction,  and  contains  chlorid  of  sodium,  traces  of  phos- 
phate of  lime,  a  small  quantity  of  dissolved  animal  matter, 
and  a  free  acid.  This,  according  to  the  experiments  of 
39 


458  ORGANIC    CHEMISTRY. 

Berard  and  Barreswil,  is  the  lactic  acid.  The  animal  matter 
appears  allied  to  the  proteinc  compounds,  and  has  been  called 
pepsinc ;  but  is  probably  not  a  distinct  substance.  The 
gastric  juice  has  a  remarkable  solvent  power ;  muscular  fibre, 
coagulated  albumen,  and  various  other  substances  are  com- 
pletely dissolved  by  it.  This  property  is  riot  confined  to  the 
gastric  juice  while  in  the  stomach  ;  when  taken  from  the  body 
it  produces  the  same  effect,  if  kept  at  the  temperature  of  the 
system,  (about  100°  F.)  If  it  is  heated  for  a  short  time  to 
200°  F.,  this  solvent  power  is  completely  destroyed ;  the 
same  effect  is  produced  by  neutralizing  the  free  acid,  but  a 
small  portion  of  any  acid  restores  its  activity.  The  solvent 
power  of  the  gastric  juice  appears  then  to  be  due  to  the  con- 
joined influence  of  the  acid  and  animal  matter.  As  the 
activity  of  this  last  is  immediately  destroyed  by  boiling  water, 
alcohol,  and  some  other  antiseptic  agents,  it  has  been  sup- 
posed to  be  a  proteinc  body  in  a  state  of  change,  (907,)  and 
the  process  of  digestion  is  regarded  as  a  kind  of  fermentation, 
induced  by  this  substance  with  the  aid  of  an  acid.  The 
change,  however,  appears  scarcely  analogous  to  any  phe- 
nomena of  this  kind,  and  although  this  idea  is  probably  the 
nearest  approximation  to  the  truth,  the  subject  is  still  obscure. 

921.  rhc  Salira. — This  fluid  contains  a  peculiar  animal 
matter  which  has  been  called  ptyahne,  with  a  considerable 
portion  of  saline  matter;  this  consists  principally  of  chlorids 
of  potassium  and  sodium,  and  the  trilasic  phosphate  of  soda, 
to  which  the  alkaline  reaction  of  the  secretion   is  due.     In 
addition  to  these  are  found  small  quantities  of  earthy  phos- 
phates and  a  trace  of  sulphocyanid  of  potassium.    The  saliva 
appears,  like  the  gastric  juice,  to  have  a  solvent  power  on 
animal  substances,  and  seems   to  prepare  the  food  for  the 
process  of  digestion.     The  pancreatic  fuid  resembles  the 
saliva  in  composition,  but  nothing  definite  is  known  as  to  its 
uses  or  properties. 

THE    BILE. 

922.  This  fluid  is  a  secretion  of  the  liver,  and  is  found  in 
the  gall-bladder.     It  is  viscid,  has  a  greenish-yellow  color, 
and  an  alkaline  reaction.     Bile  consists  of  the  soda  salt  of  a 
peculiar  fatty  acid,  with  a  small  portion  of  a  crystalline  fat 
called  cholesterine,  and   a  peculiar  coloring   matter.     This 
acid  is  called  the  choleic,  and  bile  is  a  solution  of  choleate 
of  soda. 


THE   URINE.  459 

923.  The  bile  and  the  other  alkaline  choleates  have  the 
characters  of  soaps,  and  the  use  of  this  liquid  in  removing 
oil  stains   depends  upon  this  property.     Its  composition  is, 
however,  very  different  from   that  of  the  oily  acids   before 
described,  as  it  contains  nitrogen  and  sulphur.     The  formula 
which  has  been  given  is  C44H35NO12,  but  as  taurine,  a  product 
of  its  decomposition,  has  recently  been  found  to  contain  a 
large  amount  of  sulphur,  this  must  be  modified. 

The  acid  is  slightly  soluble  in  water,  but  readily  in  alcohol. 
When  boiled  with  hydrochloric  acid  it  is  decomposed  and 
affords  a  number  of  new  substances. 

924.  This  fluid  appears  to  perform  an  important  part  in 
digestion ;  it  mixes  with  the  food  in  the  duodenum,  and  ap- 
parently aids  in  the  elaboration  of  the  chyle.     It  is  probable 
that,  by  its  peculiar  properties,  it  renders  the  fatty  portions  of 
the  food  soluble,  and  it  is  supposed  by  some  that  it  has  the 
power  of  converting  starch  and  sugar  into  fat.     This,  how- 
ever, requires  proof.     Its  presence  appears  essential  to  the 
assimilation  of  food ;  if  the  duct  which  conveys  the  bile  to 
the  duodenum  is  divided,  and  an  artificial  outlet  is  provided 
for  it,  the  secretion  is  performed  as  before,  yet  the  animal 
becomes  emaciated  and  dies,  apparently  from  imperfect  nu- 
trition.    Still,  this  fluid  appears  to  be,  to  a  great  extent,  an 
excretion  of  the  system. 

THE    URINE. 

925.  This  excrementitious  fluid,  which  is  separated  from 
the  blood  by  the  action  of  the  kidneys,  is  a  medium  for  the 
removal   of  various  saline  and  azotized   matters  which  are 
unfitted  for  the  purposes   of  life.     The  organic  substances 
thus  discharged,  are  urate  of  ammonia,  uifea,  and  hippuric 
acid.     The  urinary  secretion  of  birds,  regies,  and  insects, 
which  is  white  and  solid,  is  principally  urate  of  ammonia. 
That  of  herbivorous  animals  contains  urea  and  a  large  quan- 
tity  of  hippuric    acid,    which    in  the   carnivora  is   entirely 
replaced  by  urea  and  a  little  uric  acid.     This  is  nearly  the 
composition   of  that   of  man,  subsisting   on   a    mixed    diet. 
The  average  proportion  of  urea  in   healthy  human  urine  is 
about  three  per  cent.,  but  is  varied   by  many  causes.     The 
amount  of  uric  acid  is  about   10166    of  the  urine ;  in  addition 
to  these,  it  contains  a  small  portion  of  hippuric  acid  and  an 
organic  coloring  matter.      The    saline    matters   generally 


460  ORGANIC    CHEMISTRY. 

amount  to  two  or  three  per  cent.,  and  consist  of  chlorid  of 
sodium,  sulphates  and  phosphates  of  potassa  and  soda,  with 
traces  of  ammoniacal  salts,  and  phosphates  of  lime  and  mag- 
nesia. Fresh  urine  has  an  acid  reaction,  which  is  ascribed 
to  the  uric  acid  that  is  held  in  solution  by  the  phosphate 
of  soda.  Pure  urine  undergoes  no  change  by  keeping,  but 
when  in  contact  with  the  mucus  of  the  bladder  it  is  rapidly 
decomposed,  and  the  urea  is  converted  into  carbonate  of 
ammonia,  (^74.) 

926.  In  diseased  states  of  the  system  the  composition 
of  this  fluid  is  sometimes  altered,  and  the  uric  acid  or 
earthy  salts  rendered  less  soluble  or  more  abundantly 
secreted,  are  deposited  in  the  bladder,  forming  stony  concre- 
tions or  calculi.  They  are  most  frequently  uric  acid  or 
u rates,  and  the  phosphates  of  lime  and  magnesia ;  oxalate 
of  lime  frequently  occurs  in  this  form,  although  oxalic  acid 
docs  not  exist  in  healthy  urine. 

THE  BRAIN  AND  NERVOUS  MATTER. 

921.  These  substance  have  a  close  resemblance  in  their 
organization  and  chemical  composition  ;  the  white  and  gray 
portions  of  the  brain  differ  principally  in  their  structure. 
The  brain  contains  about  twenty  per  cent,  of  solid  matter, 
the  rest  is  water.  About  one-third  of  the  solid  substance 
resembles  albumen  ;  the  remainder  is  composed  of  several 
fatty  substances,  some  of  which  are  quite  peculiar  in  their 
composition,  from  containing  nitrogen  and  phosphorus  ;  the 
amount  of  this  last  element  is  about  four  per  cent,  of  the 
solid  matter.  The  cerebric  acid  is  obtained  in  white  crys- 
talline grains,  and  forms  very  insoluble  salts.  The  oleo- 
phosphoric  acid  is  a  compound  of  phosphoric  acid  with  an 
oil  resembling  o^nc,  and  is  decomposed  into  these,  by  long 
boiling  with  water.  The  cerebral  substance  contains  besides 
these,  the  crystalline  fat  found  in  the  bile,  cholcsferine,  and 
some  other  substances  which  have  not  been  thoroughly  studied. 
The  fatty  matter  of  the  blood,  consists  in  part  of  cholesterine 
and  a  substance  which  contains  nitrogen  and  phosphorus, 
and  is  analogous  to  cerebric  acid. 

MTLK. 

928.  This  secretion  designed  for  the  use  of  the  young 
animal,  contains  all  the  substances  necessary  for  its  proper 


TONES.  461 

developement.  The  proportion  of  its  ingredients  is  very 
variable,  but  the  following  analysis  of  cows'  milk  may  be 
taken  as  an  average ;  1000  parts  contain  water  873  ;  butter 
30  ;  caseine  48-2  ;  milk  sugar  43-9  ;  phosphate  of  lime  2-3  ; 
chlorids  of  potassium  and  sodium  1*68,  with  smalt  quantities 
of  phosphates  of  iron  and  magnesia,  besides  soda  in  combi- 
nation with  caseine.  These  substances  have  been  already 
described  under  their  separate  heads.  Human  milk  contains 
proportionably  more  sugar,  but  does  not  differ  in  other  re- 
spects. That  of  carnivorous  animals  contains  caseine  and 
butter,  but  no  sugar,  and  corresponds  to  their  food,  which 
consists  of  proteine  compounds  and  fat. 

BONES. 

929.  Bones  consist  of  a  tissue  of  cartilaginous  substances 
enveloping  a  large  quantity  of  earthy  salts.     Those  of  adult 
animals  usually  afford   from   thirty-seven  to  forty-two  per 
cent,  of  organic  matter,  which  is  principally  dissolved   by 
boiling  water,  and  constitutes  gelatine.     The  earthy  matter, 
varying   from    fifty-eight  to   sixty-three   per  cent.,  is   prin- 
cipally phosphate  of  lime.     The  following  analyses  are  from 
Berzelius : 

Human  Bones.  Ox  Bones. 

Animal  matter  dissolved  by  boiling,     -        -        32-17  (  33.30 
Insoluble  vascular  substance,        -        -        -           1-13  J 

Phosphate  of  lime  with  a  little  fluorid  of  calcium,  53-04  57-35 

Carbonate -of  lime, 11-30  3-85 

Phosphate  of  magnesia,        -         -         -         -  1-16  2-05 

Soda  and  chlorid  of  sodium,          -         -        -  1-20  3-45 

100-00     100-00 

The  phosphate  of  lime,  according  to  thj^tatest  researches 
of  Berzelius,  is  the  tribasic  phosphate,  3Ca(flrO5.  The  bones 
of  infants  contain  comparatively  less  earthy  matter  than  those 
of  adults,  and  the  same  fact  is  observed  in  rickets  and  some 
other  diseases  connected  with  defective  nutrition. 

930.  The  teeth  have  a  composition  very  similar  to  bones, 
but  the  quantity  of  organic  matter  is  less.     The  skeletons  of 
mollusca  and  of  zoophytes,  are  composed  of  animal  matter 
with  carbonate  of  lime,  and  small  traces  of  phosphates  of 
lime  and  magnesia  with  fluorid  of  calcium. 

39* 


4-62  ORGANIC    CHEMISTRY. 

NUTRITION    OF    PLANTS    AND    ANIMALS. 

931.  The  animal  creation  rs  entirely  dependent  for  its 
support  upon  the  products  of  the  vegetable.  Plants  assimi- 
late inorganic  matter,  and  give  it  a  form  which  fits  it  for  the 
support  of  animals.  We  may  then  properly  consider  first, 
the  nutrition  of  vegetables.  The  organic  substances  essential 
to  plants  are  cellulose  and  proteinc ;  these  enter  into  the 
structure  of  the  smallest  vegetable,  and  are  necessary  to  the 
formation  of  cells,  which  are  the  first  rudiments  of  organic 
developement.  Besides  these,  plants  may  contain  sugar,  oils, 
acids,  and  resins,  but  these  are  not  necessary  to  their  con- 
stitution. 

93'^.  The  proteine  compounds  contain  small  portions  of 
sulphur  and  phosphorus,  and  the  ligneous  fibre  is  never 
destitute  of  inorganic  salts ;  these  are  always  found  dissolved 
in  the  fluids  of  the  plants,  and  are  essential  to  its  perfect 
developement.  Some  of  them  are  decomposed  by  the  plants, 
to  furnish  sulphur  and  phosphorus  for  the  albumen  and  other 
proteine  bodies,  but  beyond  this,  little  is  known  of  the  func- 
tions of  these  substances.  The  seeds  of  vegetables  contain 
starch  and  proteine,  which  serve  for  the  nourishment  of  the 
plant  until  its  organs  are  sufficiently  developed  to  enable 
it  to  support  itself  from  external  sources. 

933.  The  food  of  plants  consists  of  carbonic  acid,  water, 
and  ammonia,  in  addition  to  tin-  mineral  salts  already  men- 
tioned.    These  are  absorbed  by  the  organs  of  the  vegetable, 
and  are  converted  into  cellulose  and  proteine ;  the  power  by 
which  this  is  effected  is  unknown ;  chemical  affinity  is  con- 
trolled and  directed  by  the  agency  of  life  so  as  to  produce 
complex  and  highly  organized  bodies.     We  know,  however, 
the  substances  which  enter  into  combination,  and  the  results 
of  their  action ;  in  this  way  the  formation  of  these  bodies 
may  be  expressed  by  formulas. 

934.  The  cellular  tissue  is  formed   from  the  elements  of 
carbonic   acid    and    water,    by   the   separation   of  oxygen ; 
twelve  equivalents  of  carbonic  acid,  with  ten  equivalents  of 
water;  Ci2O24-f-H10Ow=CI2Hi0Oi0+ 10O ;  or  one  equivalent 
of  cellulose  and  ten  of  oxygen.     In  the  formation  of  proteine, 
the  elements  of  ammonia  are  added  to  those  of  carbonic  acid 
and  water.     Forty  equivalents  of  carbonic  acid  with  fifteen  of 
water  and  five  of  ammonia  =  one  equivalent  of  proteine  and 
eighty-three  of  oxygen.     It  has  been  shown  (910)  that  pro- 


NUTRITION   OP    PLANTS   AND   ANIMALS.  463 

teine,  under  certain  circumstances,  absorbs  oxygen,  and  is 
decomposed  into  ammonia  and  humic  acid.  This  last  is 
formed  from  woody  fibre,  by  the?  loss  of  the  elements  of 
water  and  carbonic  acid  ;  proteine  may  therefore  be  pro- 
duced from  cellulose,  by  adding  ammonia  and  subtracting 
carbonic  acid  and  water. 

935.  All  the  other  principles  of  plants  may  be  formed  in 
a  similar  manner.     Starch  is  identical  in  composition  with 
cellulose,  and   yields  sugar  and  gum  by  combining  with- the 
elements  of  water.     Malic  acid  is  formed  from  the  elements 
of  eight  equivalents  of  carbonic  acid  and  four  of  water,  by  the 
abstraction  of  twelve  equivalents  of  oxygen,  and  the  other  acids 
are  produced  by  an  analogous  process.     It  is  probable  that 
the  saline  and  alkaline  matters  in  the  sap  exercise  some 
influence  on  these  processes,  and  conduce  to  the  formation 
of  the  various  products. 

936.  The  oxygen  which  is  set  free  in  all  these  reactions 
is  evolved   from  the  leaves  in  the  form  of  gas.     If  a  branch 
of  any  plant  is  placed  under  an  inverted  receiver,  filled  with 
pure  water,  and  exposed  to  the  sun's  light,  small   bubbles  of 
gas  will  appear  on  the  leaves,  which  rise  and  collect  in  the 
upper  part  of  the  jar.     This  gas   is   pure  oxygen,  and  is 
evolved  by  all  healthy  plants  when  exposed  to  the  light ;  in 
darkness  the   process  of  nutrition   is  very  imperfectly  per- 
formed, and  the  carbonic  acid  absorbed  by  roots  is  given  off 
from  the  leaves  unchanged.     If  a  plant  is  made  to  grow  in 
a  vessel   containing  a  mixture  of  common  air  and   carbonic 
acid  gas,  the  latter  will  be  slowly  absorbed  and   replaced  by 
pure  oxygen.     Plants   have  the  power  of  absorbing  gaseous 
carbonic  acid  and  water  through  their  leaves,  as  well  as  by 
their  roots ;  they  also  exhale  large  quantities  of  water  from 
the  pores  on  the  surface  of  the  leaves. 

937.  A  soil    fitted  for  the  growth  of  plants,  must  contain 
in  a  soluble  form  all  the  salts  and  mineral  constituents  which 
they  require.     These  vary  in  different   plants ;  their  nature 
and    quantity    are   determined    by  minute   analyses   of  the 
ashes  of  each  vegetable.     The   most  important  are  potash, 
lime,  magnesia,  and   iron,  combined   with   sulphuric,   phos- 
phoric and    silicic   acids,   and    chlorine.      Plants    have  the 
power  to  decompose  these  salts ;  we  have  observed  that  they 
separate  sulphur  and   phosphorus  to  form  the  proteine  com- 
pounds, and  all  of  them  contain  salts  of  potash  with  vegetable 
acids,  as  in  the  grape,  (808.)     The  alkali  in  these  has  been 


464  ORGAJfIC    CHEMISTRY. 

separated  from  its  combination  with  the  mineral  acids ;  when 
the  plant  is  burned,  these  salts  are  decomposed,  and  produce 
the  carbonate  of  potash,  which  the  ashes  of  vegetables  always 
contain,  (505.) 

938.  Many  of  the  mineral  substances  are  contained  in  the 
rocks,  from  whose  disintegration  the  soil  was  formed,  and 
their   slow   decomposition    gradually    liberates    them    in   a 
soluble   form.     Often,   however,  by   long  cultivation,   some 
particular  ingredients  of  the  soil   become  exhausted,  and  it  is 
no  longer  productive.     Its  fertility  may  then  be  restored  by 
the  application  of  some  mineral  manures,  as  wood-ashes,  or 
bone-dust.     A  soil  which  has  become  unfitted  for  the  growth 
of  one  plant,  may  still  contain  the  substances  necessary  to 
the  support  of  another,  and   hence  the  utility  of  rotation  in 
crops.     The  ashes  of  tobacco  contain  a  large  amount  of 
potash,    while   wheat   and   other   cereal    grains   abound    in 
phosphate  of  lime ;  so  that  a  soil  well  adapted  to  the  growth 
of  tobacco  may  not  be  suited  to  wheat,  and  vice  versa. 

939.  Fertile  soils  generally  contain,  in  addition  to  these, 
a  portion   of  humus    from   the  decomposition   of  vegetable 
matter.     This  is    beneficial   by  its  slow  decomposition,  by 
which   it   is  constantly  evolving  carbonic  acid,  and   by  the 
ammonia  that  it  contains.     It  thus  presents  a  constant  source 
of  these  substances  to  the  roots  of  plants.     We  have  stated 
that   humic  acid,   or  humus,  not   only  combines   with  the 
ammonia  of  the  atmosphere,  but  is   able  to  form   it  by  the 
direct  absorption  of  nitrogen,  (785.)     Many  chemists  main- 
tain that  humic  acid   itself  constitutes  a  part  of  the  food  of 
plants,  and  that  it  combines  with  the  elements  of  water  and 
ammonia  to  generate  the  various  products  of  the  vegetable 
organism.     This  view  has  been  ably  defended,  but  we  have 
no  evidence  that  it  is  absorbed  by  plants,  while  it  is  certain 
it  is  not  necessary  to  their  growth.     There  are  many  plants 
which  are  capable  of  growing  without  any  connection  with 
the  soil ;  they  may  be  suspended  from  the  ceiling,  and  will 
continue  to  grow  luxuriantly  for  years.     In  these  plants  the 
process  of  nutrition  is  apparently  the  same  as  in  those  which 
derive  their  support   from  the  earth.     They  absorb  carbonic 
acid,  ammonia  and  water,  from   the  atmosphere,  and   form 
ligneous  fibre  and  proteine  like  other  plants.    The  amount  of 
mineral  matter  which  they  contain  is  small,  and  is  doubtless 
derived  from  dust   constantly  floating   in    the   atmosphere, 
which  collects  upon  the  leaves,  and  is  dissolved  and  absorbed. 


NUTRITION    OF    PLANTS    AND    ANIMALS.  465 

We  have  here  vegetables  subsisting  entirely  upon  the  in- 
gredients of  the  atmosphere,  and  the  results  of  experiment 
seem  to  show  that  all  plants  are  nourished  by  the  same 
substances,  and  that  the  only  agency  of  humus  is  to  afford 
carbonic  acid  and  ammonia. 

940.  From  what  has  been  stated,  it  is  easy  to  understand 
why  ammoniacal  salts  are  such  efficient  fertilizers  of  the  soil. 
Plants  watered  with  a  weak  solution  of  the  sulphate,  or  any 
other  salt  of  ammonia,  grow  very  rapidly,  and   often  attain 
twice  the  size  and  strength  of  those  growing  without  this 
treatment.     The   beneficial  effects  of  guano   and   urine  are 
due,  in  part,  to  the  ammonia  which  they  afford.     Guano  con- 
sists in  the  excrements  of  sea-birds  which  resort  in  great  num- 
bers to  small   rocky  islands  on   the  coast  of  South  America 
and  Africa.     The  recent  excretion  consists  of  urate  of  am- 
monia, with  various  inorganic  salts,  but  the  uric  acid  is  gradu- 
ally decomposed  and   affords  oxalate  of  ammonia.     Wheat 
manured  with  guano  is  found  to  contain  a  quantity  of  azotized 
matter,  twice  as  great  as  that  raised  on  the  same  soil  without 
any  manure  ;  this  is  attributable  principally  to  the  absorption 
of  the  ammonia. 

941.  The  food  of  both   herbivorous  and  carnivorous  ani- 
mals consists  of  proteine  in   its  various   forms,  with  starch, 
sugar,  fat,  and   gelatine.     Those   subsisting   on  vegetables, 
appropriate   the   albumen   and    fibrine   which    these   bodies 
contain,  for  the  formation  of  muscular  tissues,  that  finally 
become   the    food    of  carnivorous   animals.      The   proteine 
compounds,  which  alone  can  form  blood  and  muscle,  are  ob- 
viously distinguished   from  the  non-azotized  substances  that 
constitute   a   large   portion    of  the   food  of  many  animals. 
Liebig  conveniently  designates  them  as  the  Elements  of  Nu- 
trition, while  gelatine  and   all   non-azotized   food  are  called 
Elements  of  Respiration,  as   they  are  supposed  to  be  in  a 
great  measure  consumed  in  that  process. 

942.  The  nature  of  the  digestive  process  has  been  already 
noticed,  (920.)     The  substances  taken  as  food  are  reduced 
by  the  fluids  of  the  stomach  to  a  state  of  solution.     They 
then  pass  into  the  small  intestines,  where  the  lacteals  take  up 
the  portions  which  have  been  rendered  soluble,  and  fitted  for 
the  purposes  of  nutrition.     The  saccharine  and  farinaceous 
portions  of  the  food  have  never  been  observed  in  the  chyle, 
but  the  blood,  shortly  after  the  saccharine  substances  have 
been   taken   into  the  stomach,  contains  a  very  appreciable 


466  ORGANIC    CHEMISTRY. 

quantity  of  them.  It  is  well  known  that  water  and  saline 
fluids  arc  directly  absorbed  by  the  blood-vessels  of  the 
lining  membrane  of  the  stomach,  and  it  is  probable  that 
alimentary  substances  in  a  state  of  complete  solution  arc 
taken  into  the  circulation  in  the  same  manner.  These  soon 
disappear  from  the  blood,  and  arc  supposed  to  be  oxydized 
in  the  lungs. 

943.  The  non-azotized  matters  taken  into  the  stomach  are 
probably  in  part  converted  into  fat.     The  most  complete  and 
satisfactory  experiments  have  proved,  that  fat  is  really  formed 
in  the  system,  and  is  not,  as  was  formerly  supposed,  derived 
from  that  contained  in  the  food.     Geese   fed  upon  corn,  are 
found  to  secrete  an  amount  of  fat   much  greater  than  is  con- 
tained in  the  maize  eaten  by  them,  and  bees  form  wax  if  fed 
upon  sugar.     We  are    indeed  able  to   form  one  of  the  fatty 
acids  of  butter,  (butyric  acid,)  from  starch  or  sugar  by  fer- 
mentation.    It  is  only  by  supposing  it  to  be  formed  in  the 
alimentary  process,  that  we  can  account  for  the  constant  pre- 
sence of  fat  in  the  chyle. 

The  proteinc  compounds  in  the  chyle  require  merely  the 
organizing  power  of  the  vital  force  to  give  them  the  form  of 
muscular  tissue 

944.  In  th     living  body  there  is  a  constant  waste  of  the 
tissues ;    the  chemical   forces,  aided   by  the  agency  of  the 
oxygen  of  the  air,  are  producing  a  transformation  of  the  mus- 
cular and   adipose  substances   into  simpler  products,  which 
are  excreted  from  the  body  in  various  ways.     Baron  Liebig 
has  shown  that  a  simple  relation  exists  between  the  compo- 
sition of  the  muscular  fibre  and  the  elements  of  the  bile  and 
urine ;  so  that  choleic  acid  and  urea  may  be  formed  from  it, 
by  the  addition  of  a  little  oxygen.     The  urea  and  uric  acid 
contain  the  more  azotized  portions,  and  the  bile  those  which 
arc  rich  in  carbon.    The  fatty  tissues  on  the  contrary  appear 
to   be  completely  converted   into  carbonic  acid  and  water. 
The  object  of  nutrition  is  to  preserve  the  equilibrium  of  the 
system  by  supplying  the  waste  of  the  tissues,  and  so  long  as 
this  balance  is  maintained,  the  organism  is  in  a  healthy  con- 
dition.    When  the  amount  of  non-azotized  food   is  greater 
than  is  consumed  in  the  process  of  respiration,  the  excess  is 
secreted  in  the  form  of  fat,  and  sometimes  increases  to  an 
enormous  extent,  as   is   seen    in   the    fattening  of  domestic 
animals.     If,  however,  the  supply  is  stopped,  the  reverse 


NUTRITION    OF    PLANTS    AND    ANIMALS.  467 

process  commences ;  the  secreted  fat  is  taken  into  the  system 
and  oxydized,  and  as  there  is  no  way  to  supply  its  loss,  is 
soon  completely  absorbed. 

945.  The  act  of  respiration  has  for  its  object  to  bring  the 
blood  into  contact  with  the  oxygen  of  the  atmosphere.     In 
the  higher  orders  of  animals,  this  is  accomplished  through 
the  lungs.     These  organs  have  a  cellular  structure,  and  are 
composed  of  a  great  number  of  cavities  capable  of  inflation 
with  air.     Over  the  surfaces  of  these  are  spread  the  minute 
branches  of  the  pulmonary  artery,  and  the  blood  is  conse- 
quently brought  into  close  contact  with  the  air.     In  the  pro- 
cess oxygen  gas  is  absorbed,  and  carbonic  acid  gas  expelled. 
The  relative  proportions  which  the  oxygen  absorbed,  and  the 
carbonic  acid  exhaled,  bear  to  one  another,  are  determined  by 
the  law  of  the  mutual  diffusion  of  gases  already  mentioned, 
(132.)     By  this  law,  the  volumes  of  any  two' gases  which 
pass  through  a  porous  medium  to  mingle  with  each  other, 
will  be  in  the  inverse  proportion  of  the  square  roots  of  their 
specific  gravities.    The  volume  of  oxygen  that  passes  inward, 
will  exceed  that  of  the  carbonic  acid  which  passes  outward, 
in  the  proportion  of  1174  to  1000.    As  carbonic  acid  contains 
exactly  its  own  volume  of  oxygen,  it  follows  that  174  parts 
or  nearly  fifteen  per  cent,  more  of  oxygen  are  absorbed  by 
the  lungs  than  are  given  out  in  the  form  of  carbonic  acid. 
A  portion  of  this  excess  of  oxygen  unites  with  the  sulphur 
and  phosphorus  of  the  original  components  of  the  body,  con- 
verting them  into  sulphuric  and  phosphoric  acids,  and  the 
remainder  probably  combines  with  the  hydrogen  of  the  fatty 
matter  to  form  part  of  the  water  which  is  exhaled  from  the 
lungs. 

946.  The  changes  produced  upon  the  blood  by  respiration 
have  been  already  described,  (917.)    This  process  is  essential 
to  life,  and  even  in  the  lower  orders  of  marine  animals,  is 
effected  through  the  aid  of  oxygen  dissolved  in  the  water. 
Experiments  have  shown  that  the  amount  of  carbon  given 
off  from  the  lungs  by  a  full-grown  man,  is   about  seven 
ounces  in  twenty-four  hours.     This  oxydation,  or  slow  com- 
bustion of  carbon,  must  necessarily  evolve  heat,  and  is  doubt- 
less one  source  of  the  heat  of  the  animal  system ;  but  the 
temperature  of  living  animals  is  due  in  part  to  the  other 
changes  which  are  going  on  in  the  organism.    In  some  cases 
of  disease,  when  the  respiratory  function  has  been  almost 


468  ORGANIC    CHEMISTRY. 

entirely  suspended  for  hours,  the  temperature  of  the  body 
has  remained  undiminished. 

947.  Vegetables  have  to  a  certain  extent  the  power  of 
maintaining  a  temperature  above  that  of  the  atmosphere ; 
this  is  particularly  observed  in  the  leaves  and  young  shoots, 
where  vegetation  is  most  active.     In  the  flowering  of  some 
species  of  Arum,  a  thermometer  placed  among  the  spadiccs 
has  been  observed  to   rise  to  121°,  when  the  temperature  of 
the  atmosphere  was  only  66°.     Experiments  have  shown  that 
in  this  case  it  is  due  to  the  absorption  of  oxygen,  but  it  is 
hardly  probable  that  such   is  the  general  cause.     When  we 
consider  that  heat  is  evolved  in  very  many  changes  which 
are  often  independent  of  the  absorption  of  oxygen,  there  is 
no  difficulty  in  accounting  for  its   production  in  the  processes 
of  nutrition  and  assimilation. 

948.  It  is,  however,  true  that  in  health,  the  oxydation  of 
carbon   may  be  taken  as  a   measure  of  the   heat  evolved. 
The  inhabitants  of  Greenland  and  other  northern  countries 
consume  in  their  food  immense  quantities  of  fat  and  oil,  and 
voyagers  in  these  regions,  have  found  such  a  diet  not  only 
healthful,  but  even  necessary,  to  enable  them  to  endure  the 
intense  cold  to  which  they  were  exposed. 

949.  In   those   animals  which  subsist  entirely  upon  flesh, 
the  amount  of  oxygen  absorbed  is  not  less  than  in  the  herbi- 
vorous, and  the  oxydizing   process   is  at  the  expense  of  the 
muscular  tissue.     The  waste  of  this  is  consequently  much 
greater  than  in  those  animals  subsisting  upon  a  mixed  diet, 
the   fat   and   starch   of  which  supply  the   demands  of  the 
respiratory  process. 

950.  The   lifeless    particles   of  the   inorganic  world    are 
assimilated  by  plants  from   the  atmosphere,  the  soil,  and  the 
waters.     Once  taken   into  their   structure,  they   arc    trans- 
formed by  the  vital  force  into  woody  fibre,  starch,  sugar,  and 
proteine,  which    afford   the    materials    for   the  nutrition   of 
animals,  and  supply  the  constant  demand  of  the  respiratory 
functions.     By  the  regular  processes  of  life  these  are  again 
set  free  in  their  original   forms  of  carbonic  acid,  ammonia, 
and  water,  and  are  once  more   ready  to  enter  the  upward 
current  of  organic  life. 

By  a  beautiful  adjustment  of  these  organic  forces,  the 
balance  of  the  two  great  kingdoms  of  nature  is  maintained. 
The  carbonic  acid  set  free  by  the  processes  of  combustion, 


NUTRITION   OF   PLANTS   AND    ANIMALS.  469 

and  the  respiration  of  animals,  fails  to  vitiate  the  purity  of 
the  atmosphere,  because  the  vegetable  kingdom  appropriates 
all  the  carbon  of  this  gas  for  its  own  support,  and  restores 
an  equal  volume  of  pure  oxygen  to  the  air. 

The  mind  rests  with  equal  pleasure  and  admiration  on 
these  beautiful  laws,  which  silently,  but  unceasingly,  work 
out  an  expression  of  the  Almighty  Will. 

40 


INDEX. 


###  The  references  are  to  the  numbers  of  the  sections 


ACETATES,  725. 

Acetene,  710. 

Acetone,  733. 

Acetic  acid,  quick  process  for,  722. 

Acetic  ether,  732. 

Acetic  amylic  ether,  743. 

Acid,  acetic,  720;  acetonic,  814; 
aconitic,  816;  adipic,  803;  an- 
amirtic,  800;  antimonic,  624; 
antimonious,  624  ;  arsenic,  629 ; 
arsenious,  628 ;  benzoic,  755 ; 
boracie,  370 ;  bromic,  274 ;  bu- 
tyric, 794 ;  capric,  caproic,  ca- 
prylic,  795 ;  carbazotic,  763 ; 
carbolic,  763;  carbonic,  339; 
carbovinic,713;  cerebric,  927; 
chloracetic,  731 ;  chloric,  271 ; 
chlorochromic,  595 ;  chlorous, 
269;  choleic,  922;  chromic, 
593 ;  cinnamic,  764  ;  citraco- 
nic,  816 ;  citric,  815 ;  cocinic, 
797;  columbic,  612;  cyanic, 
874  ;  cuminic,  758 ;  cyanuric, 
886;  dialuric,900;  elaidic,  802; 
enanthylic,  795;  ethalic,  750; 
equicetic,  814  ;  ferric,  587  ; 
ferridcyanic,  888 ;  ferrocyanic, 
886;  fluoboric,  373  ;  fluosilicic, 
364 ;  formic,  741 ;  fulminic, 
872;  fumaric,  814;  gallic,  819; 
hippuric,  903;  humic,  785;  hy- 
driodic,  423 ;  hydrobromic,  422 ; 
hydrochloric,  416;  hydrocya- 
nic, 867 ;  hydrofluoric,  425  ; 
hydroselenic,  436  ;  hydrosul- 
phuric,  429;  hyperiodic,  278; 
nypochlorous,  267 ;  hydrotellu- 
ric,  436;  hyponitrous,  310;  hy- 
pophosphorous,  320 ;  iodic,278; 


isatinic,  839;  kinic,  850;  lac- 
tic, 772 ;  lauric,  '797 ;  malic, 
813;  maleic,  814;  manganic, 
577 ;  margaric,  798  ;  meconic, 
852  ;  metacetonic,  776 ;  molyb- 
dic,  612;  mucic,  777;  muria- 
tic, 416;  myristic,  797 ;  nitric, 
312;  nitrobenzoic,  755;  nitro- 
muriatic,420;  nitrophenisic,ni- 
tropicric,763;nitrosalicylic,762; 
nitrous,  311;  oleic,  802;  opianic, 
852 ;  osmic,737 ;  oxalic,806 ;  ox- 
alovinic,  808;  oxaluric,  902 ;  ox- 
amic,807  ;  parabanic,902 ;  para- 
taric,810;  pectic,778;  pelargo- 
nic,  795 ;  permanganic,  577  ; 
phosphoric,  324;  picric,  763; 
pimelic,803;  phosphovinic,713; 
platinocyanic,889 ;  prussic,867 ; 
pyroligneous,723 ;  racemic,812; 
saccharic,  775 ;  salicylic,  760  ; 
sebacic,  803;  selenic,  298;  se- 
lenious,  298;  silicic,  359;  stan- 
nic, 615;  stearic,  799;  suberic, 
succinic,803;  sulphamylic,744 ; 
sulphethalic,  748 ;  sulphovinic, 
711;  sulphindigotic,  838;  suK 
phocetic,  748  ;  sulphocyanic, 
880 ;  sulphomethylic,  737 ;  sul- 
phurous, 286 ;  sulphuric,  289  ; 
tannic,  817  ;  tartaric,  810 ;  tar- 
tarovinic,  811 ;  telluric,  tellu- 
rous,  299;  titanic,  612;  tung- 
stic,  612;  ulmic,  785;  uric,898; 
valeric  (valerianic),  746;  xan- 
thic,  713. 

Acids  and  alcohols,  compared,702 ; 
fatty,  list  of,  801;  vegetable, 
805. 


172 


INDEX. 


Acids,  195;  coupled,  704;  named, 
198;  monobasic,  674;  vinic, 
703;  theory  of,  485. 

Aconitine,  855. 

Acroleine,  791. 

Affinity,  chemical,  206;  circum- 
stances which  influence,  209. 

Agriculture,  chemistry  of,  937. 

Air-pump,  28. 

Air,  analysis  of,  303. 

Albumen,  animal,  908;  vegetable, 
906. 

Alcohol,  699;  products  of  its 
oxydation,  719;  amylic,  742; 
methylic  sulphur,  701. 

Alcohols  and  acids,  relations  of, 
702. 

Aldehyde,  719. 

Algaroth,  powder  of,  625. 

Ali/.arine,  830. 

Alkaloids,  8 13  ;  of  Peruvian  bark, 
850;  of  opium,  851. 

Alcargene,  897;  Alcarsine,  894. 

Allantoine,  899. 

Allotropism,  264. 

Alloxan,  899;  Alloxantine,  900. 

Alloys,  477. 

Almonds,  essential  oil  of  bitter, 
753. 

Alumina,  567;  acetate  of,  725; 
silicates  of,  570  ;  sulphate  of, 
568. 

Aluminium,  566. 

Alum,  568. 

Amalgams,  639;  Amalgamation, 
161. 

Amarine,  849. 

Ammeline,  883. 

Amides,  697. 

Ammonia,  438 ;  acetate  of,  725  ; 
bin-iodized,  695 ;  hydrosulphu- 
ret  of,  538;  oxalate  of,  698, 
807  ;  present  in  the  atmosphere, 
439  ;  trichlorinized,  395  ;  salts 
of  ammonia,  537  ;  water  of, 
442 ;  use  of  as  a  fertilizer,  940. 

Ammonium,  536 ;  salts  of,  537  ; 
chlorid  of,  sulphuret  of,  538 ; 

Ampere's  theory,  168;  — rotating 
battery,  173. 

Amygdaline,  859. 

Amylic  ether,  745. 


Amylic  alcohol,  products  of  its 
oxydation,  745. 

Amylol,  742. 

Amylether,  745. 

Amarine,  754. 

Analysis  of  organic  bodies,  682. 

Anhydrous  sulphuric  acid,  294. 

Anilene,  814,  846. 

Animals,  nutrition  of,  931 ;  food 
of,  941. 

Anthracite,  786. 

Antimony,  622  ;  compounds  with 
oxygen,  623  ;  chlorids  of,  625 ; 
glass  of,  623 ;  sulphurets  of, 
626 ;  tartrate  of,  and  potash, 
811. 

Aqua  regia,  420  ;  ammoniae,  442 ; 
fortis,  314. 

Araeometer  of  Nicholson,  42. 

Arbor,  Dianx,  651 ;  Saturni,  605. 

Argol,  810. 

Aricine,  850. 

Arsenic,  627  ;  as  a  poison,  de- 
tection of,  632;  chlorids  of, 
630 ;  compounds  of,  with  oxy- 
gen, 628 ;  Marsh's  test  for,  636 ; 
reduction  of,  634  ;  salts  of,  629  ; 
sulphurets  of,  630. 

Arseniureted  hydrogen,  631. 
\  Arsine,  895. 
I  Artesian  wells,  70. 

Asparagine,  860. 

Assafcetida,  oil  of,  826. 

Atmosphere,  chemical  history  of, 
302  ;  mechanical  properties  of, 
24;  weight  of,  31,  32;  deter- 
mination, pressure  of,  34  ;  limits 
of,  35. 

Atomic    theory,    213;    weights, 

table  of,  188. 
|  Atoms,  8;   specific  heat  of,  215; 

polarity  of,  218. 
!  Attraction  of  gravitation,  8 ;  che 

mical,  12. 
I  Atropine,  854. 

Aurum  Musivum,  617. 

Azote,  see  Nitrogen,  300. 

Balance,  37;  of  organic  forces,  950. 

Barium,  544  ;  chlorid  of,  546. 

Barometer,  33. 

Baryta,  545;  carbonate  of,  548; 
nitrate  of,  547 ;  sulphate  of,  547. 


INDEX. 


4-73 


Batteries,  galvanic,  164  ;  sustain- 
ing, 244 ;  Daniel's,  245 ;  Smee's, 
247. 

Beeswax,  800. 

Benzamide,  754  ;  Benzoine,  756. 

Benzene,  or  Benzole,  757. 

Benzoline,  754. 

Benzeline,  846. 

Benzoilol,  753 ;  chlorinized,  754 ; 
sulphureted,  753. 

Bile,  922. 

Bibasic  acids,  674. 

Bismuth,  618 ;  oxyd  of,  619 ;  ni- 
trate of,  620;  fusible  alloy,  621. 

Bituminous  coal,  786. 

Bleaching  powders,  559. 

Blood,  915. 

Blowpipe,  compound,  400;  mouth, 
468. 

Blue  pill,  639. 

Boiling,  phenomena  of,  119;  boil- 
ing-point, 119;  elevated  by 
pressure,  125. 

Bones,  929. 

Boracic  ether,  714. 

Boron,  preparation  and  properties, 
368 ;  compound  with  oxygen, 
369  ;  chlorid  of,  372  ;  fluorid  of, 
373 ;  sulphuret  of,  374. 

Borax,  532. 

Brain  and  nervous  matter,  927. 

Bread-making,  907. 

British  gum,  779. 

Bromine,  history  and  preparation 
of,  272. 

Brucine,  853. 

Butter  and  butyrine,  794. 

Butyrone,  794. 

Cadmium,  601. 

Caffeine,  856. 

Calcium,  properties  of,  551 ;  chlo- 
rid of,  554;  fluorid  of,  556; 
oxyd  of,  552. 

Calculi,  urinary,  926. 

Calomel,  641. 

Camphene,  821. 

Camphor,  824;  artificial,  820; 
Borneo,  825. 

Cane  sugar,  766. 

Caoutchouc,  827. 

Capacity  for  heat,  106. 

Capillary  attraction,  21. 
40* 


Capsicine,  855. 

^Caustic  potash,  493. 

Carbonic  acid,  liquefaction  and 
solidification  of,  137 ;  how  re- 
moved from  wells,  344 ;  of  at- 
mosphere, 345. 

Carbonic  oxyd,  347. 

Carthamine,  830. 

Carbureted  hydrogen,  heavy,  454. 
"  "  light,  451. 

Carmine,  830. 

Carbon,  properties  and  history, 
330;  bisulphuret  of,  352;  chlo- 
rids  of,  351 ;  compounds  with 
hydrogen,  449  ;  nitrogen,  354  ; 
compounds  with  oxygen,  338 ; 
oxyd  of,  347 ;  density  of  vapor 
of,  680. 

Caseine,  909 ;  vegetable  906. 

Cathode,  236. 

Catalysis,  212. 

Cassius,  purple  of,  655 

Cellular  tissue,  formation  of,  934. 

Cellulose,  781. 

Cerium,  573. 

Cetene,  749. 

Chameleon  mineral,  577. 

Charcoal,  335 ;  absorbs  gases,  336 ; 
and  odors,  337. 

Chlorophyle,  831. 

Chemical  affinity,  206;  attraction, 
12;  nomenclature,  193;  philo- 
sophy, 182. 

Cinchona  bark,  850. 

Cinnamol,  764. 

Cinchonine,  850. 

Chloranile,  842.  [845. 

Chloranilene  and  bichloranilene, 

Chlorarsine,  895.. 

Chloric  ether,  739. 

Chlorine,  preparation  ana  proper- 
ties, 260 ;  allotropism  of,  264 ; 
compounds  with  oxygen,  266. 

Chlorisatine  and  bichlorisatine, 
841. 

Chloroform,  739. 

Chlorophyle,  831. 

Cholesterine,  922. 

Chondrine,  913. 

Chromium  described,  590 ;  chlo- 
rids  of,  592;  compounds  with 
oxygen,  591 ;  salts  of,  594. 


474 


INDEX. 


Cinnamol,  76-1. 

Chyle,  919. 

Classification  of  elements,  250. 

Cleavage  of  crystals,  227. 

Coal,  334,  786;  gas  from,  457; 
products  of  its  distillation,  786. 

Coal  tar,  789. 

Cobalt,  described,  598;  chlorid  of, 
598. 

Codeine,  852. 

Cohesion,  10  ;  of  fluids,  21. 

Color  of  bodies,  61. 

Coloring  matters  described^' 829; 
red,  830;  from  lichens,  832; 
yellow,  829. 

Columbium  and  columbite,  612. 

Compound  electro-magnetic  ma- 
chine, 178. 

Compounds,  named,  195. 

Combination,  mode  of,  in  organic 
bodies,  669. 

Combination,  laws  of,  184;  by 
volume,  190. 

Combustion,  a  source  of  heat,  70; 
nature  of,  461  ;  heat  of,  462 ; 
and  structure  of  flame,  459. 

Congelation,  109. 

Conine,  846. 

Convection  of  heat,  94. 

Copper,  described,  60S;  acetate 
of,  730  ;  alloys  of,  614  ;  nitrate 
of,  611;  oxyds  of,  609;  sul- 
phate of,  610. 

Cotarnine,  852. 

Corrosive  sublimate,  641. 

Coupled  acids,  704. 

Cream  of  tartar,  811. 

Cryophorous,  123. 

Crystallization,  circumstances  in- 
fluencing it, 217;  nature  of,  216. 

Crystals,  measurement  of,  228; 
primary  forms,  220. 

Cupellation,  648. 

Cyanates,  874. 

Cyanids,  866  ;  complex,  884  ;  dou- 
ble, 867. 

Current,  passage  of  in  cells  of  a 
battery,  211. 

Cyamelidc,  875. 

Cyanogen,  354,  872;  compounds 
with  bromine,  chlorine,  &c., 
871;  hydrogen,  873. 


Cyanoxsulphide,  880. 

Daniell's  battery,  245. 

Davy's  safety  lamp,  470. 

Decomposition  of  water,  235, 386. 

De  La  Rive's  ring,  170. 

Density  of  vapours,  131,  680,  37. 

Dew,  formation  of,  99;  point,  133. 

Dextrine,  779. 

Diabetic  sugar,  767. 

Diamond,  history  and  forms  of, 
331. 

Diachylon,  plaster,  804. 

Diastase,  780,  907. 

Didymium,  573. 

Diffusion  of  gases  and  vapours, 
132. 

Digestive  process,  nature  of,  920. 

Dimorphism,  233. 

Dipping  needle,  143. 

Direct  union,  677. 

Distillation,  117;  of  alcohol,  699. 
j  Dryabalanops,  825. 

Du  Fay's  hypothesis,  150. 
|  Drummond  light,  403. 
'Dutch  liquid,  454,  718. 
I  Earth's  magnetism,  143. 

Elaldehyde,  720. 

Elasticity,  18;  of  air,  26. 

Electrical  machine,  153. 

Electrical  excitement,  147;  po- 
larity, 148. 

Electricity,  conductors  of,  151 ; 
of  high  steam,  156  ;  theories  of, 
150. 

Electricity  of  chemical  action, 
158. 

Electro-chemical  decomposition, 
234;  conditions  of,  237;  mag- 
netism,166;  magnetic  telegraph, 
179;  metallurgy,  248. 

Electro-magnetic  motions,  173. 

Electro-magnets,  171. 

Electrolysis,  237  ;  order  of,  240. 

Electrode,  237. 

Electrophorus,  155. 

Electroscopes,  152. 

Elements,   defined,    14 ;   laws   of 

'  combination  and  classification, 
250,  182;  non-metallic,  classi- 
fied, 250. 

Emetic,  tartar,  811. 

Emetine,  855. 


INDEX. 


475 


Emulsine,  859. 

Epsom  salts,  563. 

Equivalents,  table  of,  188. 

Equivalent  proportions,  187. 

Equivalent  substitution,  670. 

Eremacausis,  785. 

Ethal,  748. 

Ether,  acetic,  732 ;  acetic  amylic, 
743;  benzoic,  715;  boracic, 
714;  butyric,  794;  chloric,  739; 
hydrobromic,  709 ;  hydrochlo- 
ric, 708;  hyponitrous,  710;  lu- 
miniferous,  51 ;  methylic,  738; 
nitric,  706;  nitrous,  710;  ox- 
alic, 703  ;  perchloric,  707  ;  si- 
licic, 714;  sulphuric,  715. 

Ethers,  702;  sulphureted,  716. 

Equilibrium  of  temperature,  89. 

Euchlorine,  267. 

Eudiometry,  303  ;  by  hydrogen, 
395. 

Eupione,  788. 

Evaporation,  129. 

Expansion  by  heat,  71 ;  of  solids 
and  liquids,  28,  73,74;  of  gases, 
88;  of  water,  86;  beneficial 
results  of,  87. 

Faraday's  researches  in  magnet- 
ism, 145 ;  in  liquefaction,  136 ; 
in  electricity,  236. 

Fats  and  substances  derived  from 
them,  791. 

Fattening  animals,  943. 

Feldspar,  570. 

Fermentation,  viscous,  772 ;  vi- 
nous, 770. 

Ferridcyanogen,  887. 

Ferrocyanogen,  885. 

Fertilizers,  938,  940. 

Fibre,  woody,  781. 

Fibrine,  animal  and  vegetable, 
906,  908. 

Fire  damp,  451. 

Flame,  structure  of,  459,  464; 
effects  of  wire  gauze  on,  469. 

Fluorine,  history  and  properties, 
280. 

Fluor  spar,  556. 

Fluids,  properties  of,  19. 

Formates,  741. 

Formene,  tri-chlorinized  and  tri- 
iodized,  739. 


Franklinian  hypothesis,  150. 

Freezing  mixtures,  111. 

Friction  a  source  of  heat,  70. 

Fulminates,  892. 

Fusel  oil,  742. 

Fusible  metal,  621. 

Galena,  602. 

Galleide,  819. 

Gall-nuts,  817. 

Galvanism,  158;  origin  and  dis- 
covery of,  159;  quantity  and 
intensity  in,  163. 

Galvanic  batteries,  164,  244. 

Galvanoscopes,  167. 

Gases,  laws  of,  24 ;  liquefaction 
of,  136 ;  management  of,  257 ; 
combine  by  volume,  190. 

Gasholders,  258. 

Gastric  juice,  920. 

Gelatine,  913. 

Geine,  785. 

German  silver,  597. 

Glass,  534. 

Glucinum,  573. 

Glucose,  767. 

Gluten,  906. 

Glycerides,  792. 

Glycerine,  791. 

Glycocoll,  903. 

Gold,  652 ;  oxyds  and  chlorid  of, 
654. 

Gold  wash,  655. 

Goniometer,  common,  228 ;  Wol- 
laston's,  229. 

Goulard's  extract,  727. 

Grape  sugar,  767 ;  fermentation 
of,  770. 

Graphite,  333. 

Grove's  battery,  246. 

Gum,  777  ;  elastic,  827. 

Gun  cotton,  784. 

Gunpowder,  composition  of,  513. 

Gutta  percha,  828. 

Gypsum,  555. 

Hardness,  18. 

Hare's  blowpipe,  400. 

Hare's  deflagrator,  164. 

Heat,  69  ;  communication  of,  89  ; 
absorption  of,  101;  convection 
of,  94;  conduction  of,  90;  ex- 
pansion by,  71,  82 ;  radiant,  97 ; 
sources  of,  70;  specific,  106; 


476 


INDEX. 


transmisson  of,  103  ;  latent, 
108. 

Heavy  spar,  547. 

Helicine,  864. 

Helix,  169. 

Hematine,  916. 

Hematite,  red  and  brown,  582. 

Hematoxyline,  830. 

Hemming's  safety  tube,  402. 

Henry's  coils,  magnets,  171,  175. 

Homologous  bodies,  751. 

Humus,  785. 

Hydrobenzamide,  754. 

Hydrosalimide,  759. 

Hydrochloric  amylic  ether,  743. 

Hydrochloric  methylic  ether,  735. 

Hydrogen,  preparation  and  pro- 
perties, 375 ;  nature  of,  383 ; 
acids  of,  4 13;  action  with  chlo- 
rine, 414;  arseniureted,  631; 
compound  with  boron,  458;  bro- 
mine, 422 ;  carbon,  449 ;  chlo- 
rid,  416;  fluorine,  425 ;  iodine, 
423;  nitrogen,  437;  oxygen, 
384;  phosphorus,  445;  seleni- 
um, 436;  sulphur,  429;  per- 
oxyd  of,  410. 

Hydrometer,  47. 

Hydrosulphuret  of  ammonium, 
538. 

Hygrometers,  134. 

Hypochlorite  of  lime,  559. 

Imponderable  agents,  15. 

Indigo,  835. 

Indigogene,  837. 

Induction  of  a  current  on  itself, 
175. 

Induction  of  magnetism,  140. 

Ink,  black,  817;  blue,  886. 

Insulators  of  electricity,  151. 

Intensity,  quantity,  163. 

Induced  currents,  177. 

Induction  of  electricity  on  tele- 
graph wires,  179. 

lodiform,  739. 

Iodine,  275  ;  acetate  of,  725 ;  com- 
pounds with  oxygen,  &c.,  278. 

Ions,  236. 

Iridium,  661. 

Iron,  580 ;  carbonate  of,  589  ;  fer- 
rocyanid,  885 ;  ores  of,  582 ; 
lactate  of,  774;  oxyds  of,  585; 


reduction  of  its  ores,  583 :  salts 
of,  589  ;  specular,  586 ;  sulphu- 
rets  of,  588. 

Isatine,  839  ;  isatyde,  841. 

Isomerism,  678. 

Isomorphism,  231. 

Kakodyle,  896 ;  protoxyd  of,  897. 

Kermes  mineral,  626. 

Kreasote,  787. 

Kyanite,  570. 

Kyanizing  process,  641. 

Kyanol,  789. 

Lactates,  774;  lactide,  774. 

Lactine,  768. 

Lamp,  Davy's  safety,  470;  Jack- 
son's, 467. 

Lantanum,  573. 

Laughing  gas,  305. 

Lard  oil,  804. 

Lead,  602 ;  acetate  of,  726 ;  car- 
bonate of,  606,  728 ;  chromate 
of,  595 ;  oxyds  of,  603 ;  plaster 
or  diachylon,  804  ;  precipitated 
by  zinc,  605;  sulphuret,  604. 

Leather,  913. 

Lecanorine,  833. 

Legumine,  906. 

Leiocome,  779. 

Letheon,  715. 

Leyden  jar,  154. 

Leukol,  789,  846. 

Lichens,  832. 

Light,  50 ;  properties  of,  52 ;  la- 
tent, 66 ;  sources  and  nature,  51 ; 
analysis  of,  59 ;  chemical  rays, 
65. 

Lignine,  781. 

Lignite,  785. 

Lime,  552  ;  butyrate  of,  774,  775 ; 
carbonate  of,  558 ;  chlorid  of, 
559;  lactate  of,  774;  oxalate 
of,  808 ;  phosphates  of,  557 ;  sul- 
phate of,  555. 

Liquefaction,  108;  and  solidifica- 
tion of  gases,  137. 

Liquids,  properties  of,  20. 

Lithium  and  lithia,  543. 

Litmus,  832. 

Local  action,  244. 

Lodestone,  139. 

Lunar  caustic,  651. 

Luteoline,  829. 


INDEX. 


477 


Lymph,  919. 

Magic  circle,  172. 

Magnesia,  560 ;  carbonate  of,  564 ; 
sulphate  of,  563. 

Magnesium,  560 ;  chlorid  of,  562 ; 
oxyd  of,  561. 

Magnetism,  139 ;  Magneto-elec- 
tricity, 180. 

Magnetics  and  diamagnetics,  145. 

Magnets,  141. 

Magnets,  electro,  171. 

Malachite,  green  and  blue,  608. 

Malt,  action  of  on  sugar,  780. 

Malates,  813. 

Manganese,  574 ;  chlorids  of,  578 ; 
oxyds  of,  575 ;  salts  of  579. 

Mannite,  769. 

Marble,  558. 

Margarine,  798. 

Marriotte's  law,  30. 

Marsh  gas,  451. 

Marsh's  test  for  arsenic,  636. 

Matter,  general  properties  of,  6 ; 
states  of,  16. 

Melting-points,  112. 

Mellon,  880. 

Melloni's  researches,  104. 

Melam,  880. 

Melamine,  883. 

Mercaptan,  701. 

Mercury,  638 ;  double  amide  of, 
646 ;  chlorids  of,  641 ;  amide  of, 
646;  cyanid  of,  87 1 ;  fulminate 
of,  892 ;  iodids  of,  642 ;  nitrates 
of,  644 ;  oxyds  of,  640 ;  sulphate 
of,  645  ;  sulphur ets  of,  643. 

Metacetone,  776. 

Metameric  bodies,  678. 

Metaldehyde,  720. 

Metallurgy,  electro,  248. 

Metals,  general  properties  of,  472  ; 
oxyds  of,  479;  chemical  rela- 
tions of,  478 ;  classification  of, 
487  ;  tenacity  of,  474. 

Methal,  734. 

Methylic  alcohol,  734. 

Methylic  ether,  738. 

Methen,  738. 

Microscomic  salt,  529. 

Milk,  928;  sugar  of,  768. 
Mindereus,  spirit  of,  725. 
Mokcules,  8 ;  polarity  of,  218. 


Molybdenum,  612. 

Monobasic  acids,  674. 

Mordants,  569. 

Morphine,  851. 

Mouth  blowpipe,  468. 

Murexide,  901. 

Muriatic  acid,  416. 

Mustard,  oil  of,  826. 

Names  of  elements,  193. 

Nascent  state,  210. 

Naphtha,  790 ;  naphthaline,  789. 

Narcotine,  852;  narceine,  852. 

Nervous  matter,  927. 

Neutrality  of  salts,  483. 

Newton's  fusible  metal,  621. 

Nickel  and  its  oxyds,  596;  sul- 
phate, 597. 

Nicotine,  847. 

Nitre,  511. 

Nitric  methylic  ether,  735. 

Nitrobenzene,  757. 

Nitrogen,  300 ;  compounds  with 
oxygen,  304;  determined  in 
organic  compounds,  690. 

Nitrous  oxyd,  305. 

Nitric  oxyd,  308. 

Nitranilene,  845. 

Nomenclature  and  symbols,  193. 

Nordhausen  acid,  292. 

Nutritive  substances,  905. 

Nutrition  of  plants  and  animals, 
931 ;  elements  of,  941. 

(Ersted's  law,  166. 

Oil  of  bitter  almonds,  753;  of 
mustard,  826;  of  roses,  823; 
lard,  804;  palm,  797;  potato, 
742 ;  of  cumin,  758 ;  of  cinna- 
mon, 764;  of  the  Dutch  che- 
mists, 718;  spirea,  759;  tur- 
pentine, 821 ;  wintergreen,  761. 

Oils,  volatile  or  essential,  820. 

Olefiant  gas,  454,  717  ;  with  chlo- 
rine, 456. 

Oleine,  802. 

Opium,  851. 

Orceine,  833. 

Organic  bases  or  alkaloids,  843. 

Organic  bodies  characterized,  666 ; 
general  properties  of,  662  ;  ana- 
lysis of,  663 ;  modes  of  com- 
bination in,  669. 

Organic  nature,  balance  of,  950. 


478 


INDEX. 


Orpiment,  630. 

Osmium,  637. 

Oxygen,  252. 

Oxamide,  698. 

Oxamethane,  809. 

Oxalates,  807. 

Oxalic  methylic  ether,  809. 

Ozone,  412. 

Page's  revolving  armature,  174. 

Palm  oil,  797. 

Palmatine,  792. 

Palladium,  659. 

Pancreatic  fluid,  921. 

Paranaphthalene,  789. 

Paraffine,  788. 

Peat,  786. 

Pendulums,  84. 

Peruvian  bark,  850. 

Pepsine,  920. 

Petalite,  570. 

Petroleum,  790. 

Phenol,  763. 

Phloretine,  865. 

Phloridzine,  865. 

Phocenine,  795. 

Phosgene  gas,  349. 

Phosphorescence,  68. 

Phosphorus,  376;  chlorids,  bro- 
mids,  &c.,  326 ;  compounds  with 
oxygen,  320 ; 

Phosphureted  hydrogen,  445. 

Plants,  their  nutrition,  933. 

Platinocyanids,  88&. 

Platinum,  656;  chlorids  and  oxyds, 
658 ;  power  to  cause  the  union 
of  gases,  397  ;  sponge  and  black, 
657. 

Plumbago,  333. 

Polarization  of  light,  63. 

Polarity,  electrical,  148,  163. 

Polar  attractions  in  electrolysis, 
238. 

Polymeric  bodies,  679. 

Potash,  493;  acetate  of,  725; 
carbonates  of,  505,  507 ;  chlo- 
rate, 515;  chromate  of,  594; 
cyanate,  876 ;  nitrate,  511;  salts 
of,  504 ;  sulphates  of,  508 ;  tar- 
trate  of,  811 ;  yellow  prussiate, 
885  ;  red  prussiate,  886. 

Potassium,  488, 492 ;  chlorid,  bro- 
mid,  &c,,  497;  cyanid,  867; 


compound  with  nitrogen,  503 ; 

ferridcyanid  of,  887 ;    ferrocy- 

anid,  885 ;  oxyds  of,  493 ;  sul- 

phocyanid,  880. 
Potato  oil,  742. 
Pottery,  art  of,  571. 
Pneumatic  trough,  257. 
Presence  of  a  third  body,  212. 
Prussian  blue,  886. 
Prussic  acid,  867,  885. 
Prussiate  of  potash,  885,  887. 
Prism,  its  action  on  light,  58. 
Prismatic  colors,  60. 
Proteine,  910 ;  relation  to  fibrine, 

911. 

Pseudomorphine,  852. 
Ptyaline,  921. 
Purple  of  Cassius,  655. 
Pyrometer,  81. 
Pyroxylic  spirit,  734. 
Pyroxyline,  784. 
Quantity  and  intensity,  163. 
Quercitrine,  829. 
Quicksilver,  638. 
Quinine,  850 ;  quinoline,  846. 
Radicals,  salt,  485. 
Ratsbane,  628 ;  realgar,  630. 
Red  lead,  604 ;  precipitate,  640. 
Reflection  and  refraction  of  light, 

54,  55. 

Refraction,  double,  62. 
Rennet,  909. 
Repulsion,  11. 

Residues  of  substitution,  675. 
Resin  gas,  457. 

Respiration,  945;  elements  of,  941. 
Rhodium  and  its  compounds,  660. 
Rochelle  salt,  811. 
Safety  lamp,  470. 
Sal  ammoniac,  439,  537. 
Salicine,  861. 

Salicylol  and  its  derivatives,  759. 
Salicylic  methylic  ether,  761. 
Saligenine,  saliretine,  862. 
Saliva,  921. 
Salts,  theory  of,  484 ;  neutrality 

of,  483. 

Salt,  common,  521. 
Salt-radical,  485. 
Saltpetre,  511. 
Sanguinarine,  855. 
Saxon  blue,  838. 


INDEX. 


479 


Secondary  currents,  176. 

Selenium,  296 ;  oxyd  of,  298. 

Seleniureted  hydrogen,  436. 

Serum,  915. 

Sesqui-salts,  676. 

Silica,  359. 

Silicic  ethers,  714. 

Silicon,  355  ;  compounds  of,  358 ; 
chlorid  of,  363 ;  fluorid  of,  364 ; 
sulphuret,  366. 

Silver,  647 ;  oxyds  of,  649 ;  chlorid 
of,  650 ;  nitrate  of,  651 ;  acetate 
of,  730 ;  cyanid  of,  890 ;  fulmi- 
nate of,  893. 

Smee's  battery,  247. 

Soaps,  791,  804. 

Soda,  520 ;  acetate  of,  725  ;  bibo- 
rate  of,  532 ;  carbonate  of, 
523 ;  nitrate  of,  527  ;  phosphates 
of,  528;  silicates  of,  533;  sul- 
phate of,  525. 

Sodium,  518;  chlorid  of,  521. 

Soils,  relation  of  to  plants,  937. 

Solanine,  854. 

Solids,  properties  of,  17  j  expan- 
sion of,  82. 

Solution,  208. 

Spathic  iron,  589. 

Specific  gravity,  38 ;  rule  for,  42 ; 
of  gases,  49. 

Specific  heat  of  bodies,  106. 

Spectral  impressions,  67. 

Spermaceti,  749. 

Spheroidal  state  of  bodies,  135. 

Spirea  ulmaria,  oil  of,  759. 

Spirit,  pyroxylic,  734. 

Starch,  779. 

Steam,  125;  latent  heat  of,  118; 
elastic  force  of,  126;  engine, 
128. 

Stearine,  798. 

Stearoptens,  824. 

Steel,  584. 

Strontia,  549 ;  salts  of,  550. 

Strontium,  549;  chlorid  of,  550. 

Strychnine,  853. 

Substitution,  equivalent,  670. 

Substitution  by  residues,  675. 

Succinide,  803. 

Sugar  of  lead,  726. 

Sugar  of  milk,  768. 

Sugars,  765 ;  products  of  their  de- 
composition, 770. 


Sulphamethylane,  736. 

Sulphisatine,  841. 

Sulphovinates,  705. 

Sulphovinic  acid,  products  of  its 
decomposition,  715. 

Sulphocyanates,  880. 

Sulphur,  282 ;  compounds  with 
oxygen,  285 ;  chlorid  of,  295. 

Sulphur eted  hydrogen,  429. 

Sulphuric  methylic  ether,  736. 

Surbasic  and  bisurbasic  acetate  of 
lead,  726,  727. 

Sustaining  batteries,  244. 

Symbols,  chemical,  203. 

Synaptase,  859. 

Table  of  chemical  equivalents,188. 

Tannin,  817. 

Tartar  emetic  and  tartrates,  811. 

Taurine,  923. 

Telegraph,  electro-magnetic,  179. 

Tellureted  hydrogen,  436. 

Tellurium,  299. 

Temperature  of  flame,  465;  of 
incandescence,  463 ;  equilibri- 
um of,  89. 

Thebaine,  852. 

Theine,  856 ;  theobromine,  857. 

Theories  of  electro-chemical  de- 
composition, 243;  of  electro- 
chemical action,  243;  of  sub- 
stitution, 670. 

Theory,  atomic,  213. 

Thermo-electricity,  181. 

Thermometers,  75 ;  construction 
of,  76 ;  graduation,  77. 

Thorium,  573. 

Thunder  and  lightning,  157. 

Tin,  613;  alloys  of,  614;  oxyds 
of,  615 ;  chlorids  of,  616 ;  sul- 
phurets  of,  617. 

Tissues,  waste  of  the  animal,  944. 

Titanium,  612. 

Tolu,  balsam,  764. 

Tungsten,  612. 

Turpeth  mineral,  645. 

Turpentine,  oil  of,  821. 

Ulmine,  785. 

Upas,  poison  of  the,  853. 

Uramile,  900. 

Uranite,  uranium,  607. 

Urea,  877  ;  urine,  925. 

lire's  eudiometer,  395. 

Urinary  calculi,  926. 


480 


INDEX. 


Vacuum,  29  j  Torricellian,  33. 

Valerianates,  747. 

Vanadium,  612. 

Vapor  of  alcohol,  density  of,  700. 

Vaporization,  115. 

Vapors,  maximum  density  of,  131 ; 
density  of  determined,  680. 

Vegetable  acids,  805. 

Vegetable  mould,  785 ;  principles, 
858. 

Vegetables,  nutrition  of,  931;  tem- 
perature of,  947. 

Veratrine,  855. 

Verdigris,  830. 

Vermillion,  643. 

Vinegar,  quick  process  for,  722. 

Vinic  acids,  703. 

Vinous  fermentation,  770. 

Viscous  fermentation,  772. 

Vital  force,  667. 

Vitriol,   blue,   610;    green,  589; 


oil  of,  289  ;  white,  600. 
Volatile  alkali,  441. 
Volatile  oils,  820. 
Voltaic  pile,  160;  circle,  161,162. 
Voltaism,  158. 
Voltameter,  242. 
Volume,  of  air,  30 ;  combination  ^Zirconium,  573. 

by,  190,  191. 


Water,  natural  and  chemical  his- 
tory of,  404 ;  as  a  chemical 
agent,  408;  decomposition  of, 
386-390;  voltaic,  235;  forma- 
tion of,  392,  394 ;  unequal  ex- 
pansion of,  86. 

Water-hammer,  121. 

Wax,  800. 

Weight  and  specific  gravity,  36. 

White  arsenic,  628 ;  lead,  728. 

White  precipitate,  646. 

Wollaston's  goniometer,  229. 

Wood,'  destructive  distillation  of, 
787. 

Wood  naphtha,  734. 

Wood  spirit,  734;  oxydation  of, 
740 ;  ether,  738. 

Woody  fibre,  781 ;  transformation 
of,  785. 

Xyloidine,  784. 

Yeast,  907 ;  action  of,  770. 


Yttrium,  573. 

Zaffre,  598. 

Zinc,  and  oxyd  of,  599 ;  acetate 
of,  725 ;  chlorid  and  sulphuret 
of,  600  ;  lactate  of,  774  j  vale- 
rianate  of,  747. 


THE    END. 


054 


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